cp-tree.h (flag_access_control): Declare.

[gcc.git] / gcc / cp / pt.c

/* Handle parameterized types (templates) for GNU C++.
   Copyright (C) 1992, 93-97, 1998, 1999 Free Software Foundation, Inc.
   Written by Ken Raeburn (raeburn@cygnus.com) while at Watchmaker Computing.
   Rewritten by Jason Merrill (jason@cygnus.com).

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* Known bugs or deficiencies include:

     all methods must be provided in header files; can't use a source
     file that contains only the method templates and "just win".  */

#include "config.h"
#include "system.h"
#include "obstack.h"

#include "tree.h"
#include "flags.h"
#include "cp-tree.h"
#include "decl.h"
#include "parse.h"
#include "lex.h"
#include "output.h"
#include "defaults.h"
#include "except.h"
#include "toplev.h"

/* The type of functions taking a tree, and some additional data, and
   returning an int.  */
typedef int (*tree_fn_t) PROTO((tree, void*));

extern struct obstack permanent_obstack;

extern int lineno;
extern char *input_filename;
struct pending_inline *pending_template_expansions;

tree current_template_parms;
HOST_WIDE_INT processing_template_decl;

tree pending_templates;
static tree *template_tail = &pending_templates;

tree maybe_templates;
static tree *maybe_template_tail = &maybe_templates;

int minimal_parse_mode;

int processing_specialization;
int processing_explicit_instantiation;
int processing_template_parmlist;
static int template_header_count;

static tree saved_trees;

#define obstack_chunk_alloc xmalloc
#define obstack_chunk_free free

#define UNIFY_ALLOW_NONE 0
#define UNIFY_ALLOW_MORE_CV_QUAL 1
#define UNIFY_ALLOW_LESS_CV_QUAL 2
#define UNIFY_ALLOW_DERIVED 4
#define UNIFY_ALLOW_INTEGER 8

#define GTB_VIA_VIRTUAL 1 /* The base class we are examining is
                             virtual, or a base class of a virtual
                             base.  */
#define GTB_IGNORE_TYPE 2 /* We don't need to try to unify the current
                             type with the desired type.  */

static int resolve_overloaded_unification PROTO((tree, tree, tree, tree,
                                                 unification_kind_t, int));
static int try_one_overload PROTO((tree, tree, tree, tree, tree,
                                   unification_kind_t, int));
static int unify PROTO((tree, tree, tree, tree, int));
static void add_pending_template PROTO((tree));
static int push_tinst_level PROTO((tree));
static tree classtype_mangled_name PROTO((tree));
static char *mangle_class_name_for_template PROTO((char *, tree, tree));
static tree tsubst_expr_values PROTO((tree, tree));
static int list_eq PROTO((tree, tree));
static tree get_class_bindings PROTO((tree, tree, tree));
static tree coerce_template_parms PROTO((tree, tree, tree, int, int));
static void tsubst_enum PROTO((tree, tree, tree));
static tree add_to_template_args PROTO((tree, tree));
static tree add_outermost_template_args PROTO((tree, tree));
static void maybe_adjust_types_for_deduction PROTO((unification_kind_t, tree*,
                                                    tree*)); 
static int  type_unification_real PROTO((tree, tree, tree, tree,
                                         int, unification_kind_t, int));
static void note_template_header PROTO((int));
static tree maybe_fold_nontype_arg PROTO((tree));
static tree convert_nontype_argument PROTO((tree, tree));
static tree convert_template_argument PROTO ((tree, tree, tree, int,
                                              int , tree));
static tree get_bindings_overload PROTO((tree, tree, tree));
static int for_each_template_parm PROTO((tree, tree_fn_t, void*));
static tree build_template_parm_index PROTO((int, int, int, tree, tree));
static int inline_needs_template_parms PROTO((tree));
static void push_inline_template_parms_recursive PROTO((tree, int));
static tree retrieve_specialization PROTO((tree, tree));
static tree register_specialization PROTO((tree, tree, tree));
static int unregister_specialization PROTO((tree, tree));
static tree reduce_template_parm_level PROTO((tree, tree, int));
static tree build_template_decl PROTO((tree, tree));
static int mark_template_parm PROTO((tree, void *));
static tree tsubst_friend_function PROTO((tree, tree));
static tree tsubst_friend_class PROTO((tree, tree));
static tree get_bindings_real PROTO((tree, tree, tree, int));
static int template_decl_level PROTO((tree));
static tree maybe_get_template_decl_from_type_decl PROTO((tree));
static int check_cv_quals_for_unify PROTO((int, tree, tree));
static tree tsubst_template_arg_vector PROTO((tree, tree, int));
static tree tsubst_template_parms PROTO((tree, tree, int));
static void regenerate_decl_from_template PROTO((tree, tree));
static tree most_specialized PROTO((tree, tree, tree));
static tree most_specialized_class PROTO((tree, tree));
static tree most_general_template PROTO((tree));
static void set_mangled_name_for_template_decl PROTO((tree));
static int template_class_depth_real PROTO((tree, int));
static tree tsubst_aggr_type PROTO((tree, tree, int, tree, int));
static tree tsubst_decl PROTO((tree, tree, tree, tree));
static tree tsubst_arg_types PROTO((tree, tree, int, tree));
static tree tsubst_function_type PROTO((tree, tree, int, tree));
static void check_specialization_scope PROTO((void));
static tree process_partial_specialization PROTO((tree));
static void set_current_access_from_decl PROTO((tree));
static void check_default_tmpl_args PROTO((tree, tree, int, int));
static tree tsubst_call_declarator_parms PROTO((tree, tree, int, tree));
static tree get_template_base_recursive PROTO((tree, tree,
                                               tree, tree, tree, int)); 
static tree get_template_base PROTO((tree, tree, tree, tree));
static tree try_class_unification PROTO((tree, tree, tree, tree));
static int coerce_template_template_parms PROTO((tree, tree, int,
                                                 tree, tree));
static tree determine_specialization PROTO((tree, tree, tree *, int));

/* We use TREE_VECs to hold template arguments.  If there is only one
   level of template arguments, then the TREE_VEC contains the
   arguments directly.  If there is more than one level of template
   arguments, then each entry in the TREE_VEC is itself a TREE_VEC,
   containing the template arguments for a single level.  The first
   entry in the outer TREE_VEC is the outermost level of template
   parameters; the last is the innermost.  

   It is incorrect to ever form a template argument vector containing
   only one level of arguments, but which is a TREE_VEC containing as
   its only entry the TREE_VEC for that level.  */

/* Non-zero if the template arguments is actually a vector of vectors,
   rather than just a vector.  */
#define TMPL_ARGS_HAVE_MULTIPLE_LEVELS(NODE) \
  (NODE != NULL_TREE                                            \
   && TREE_CODE (NODE) == TREE_VEC                              \
   && TREE_VEC_LENGTH (NODE) > 0                                \
   && TREE_VEC_ELT (NODE, 0) != NULL_TREE                       \
   && TREE_CODE (TREE_VEC_ELT (NODE, 0)) == TREE_VEC)

/* The depth of a template argument vector.  When called directly by
   the parser, we use a TREE_LIST rather than a TREE_VEC to represent
   template arguments.  In fact, we may even see NULL_TREE if there
   are no template arguments.  In both of those cases, there is only
   one level of template arguments.  */
#define TMPL_ARGS_DEPTH(NODE)                                   \
  (TMPL_ARGS_HAVE_MULTIPLE_LEVELS (NODE) ? TREE_VEC_LENGTH (NODE) : 1)

/* The LEVELth level of the template ARGS.  Note that template
   parameter levels are indexed from 1, not from 0.  */
#define TMPL_ARGS_LEVEL(ARGS, LEVEL)            \
  (TMPL_ARGS_HAVE_MULTIPLE_LEVELS (ARGS)        \
   ? TREE_VEC_ELT ((ARGS), (LEVEL) - 1) : ARGS)

/* Set the LEVELth level of the template ARGS to VAL.  This macro does
   not work with single-level argument vectors.  */
#define SET_TMPL_ARGS_LEVEL(ARGS, LEVEL, VAL)   \
  (TREE_VEC_ELT ((ARGS), (LEVEL) - 1) = (VAL))

/* Accesses the IDXth parameter in the LEVELth level of the ARGS.  */
#define TMPL_ARG(ARGS, LEVEL, IDX)                              \
  (TREE_VEC_ELT (TMPL_ARGS_LEVEL (ARGS, LEVEL), IDX))

/* Set the IDXth element in the LEVELth level of ARGS to VAL.  This
   macro does not work with single-level argument vectors.  */
#define SET_TMPL_ARG(ARGS, LEVEL, IDX, VAL)                     \
  (TREE_VEC_ELT (TREE_VEC_ELT ((ARGS), (LEVEL) - 1), (IDX)) = (VAL))

/* Given a single level of template arguments in NODE, return the
   number of arguments.  */
#define NUM_TMPL_ARGS(NODE)                             \
  ((NODE) == NULL_TREE ? 0                              \
   : (TREE_CODE (NODE) == TREE_VEC                      \
      ? TREE_VEC_LENGTH (NODE) : list_length (NODE)))

/* The number of levels of template parameters given by NODE.  */
#define TMPL_PARMS_DEPTH(NODE) \
  (TREE_INT_CST_HIGH (TREE_PURPOSE (NODE)))

/* Do any processing required when DECL (a member template declaration
   using TEMPLATE_PARAMETERS as its innermost parameter list) is
   finished.  Returns the TEMPLATE_DECL corresponding to DECL, unless
   it is a specialization, in which case the DECL itself is returned.  */

tree
finish_member_template_decl (decl)
  tree decl;
{
  if (decl == NULL_TREE || decl == void_type_node)
    return NULL_TREE;
  else if (decl == error_mark_node)
    /* By returning NULL_TREE, the parser will just ignore this
       declaration.  We have already issued the error.  */
    return NULL_TREE;
  else if (TREE_CODE (decl) == TREE_LIST)
    {
      /* Assume that the class is the only declspec.  */
      decl = TREE_VALUE (decl);
      if (IS_AGGR_TYPE (decl) && CLASSTYPE_TEMPLATE_INFO (decl)
          && ! CLASSTYPE_TEMPLATE_SPECIALIZATION (decl))
        {
          tree tmpl = CLASSTYPE_TI_TEMPLATE (decl);
          check_member_template (tmpl);
          return tmpl;
        }
      return NULL_TREE;
    }
  else if (DECL_TEMPLATE_INFO (decl))
    {
      if (!DECL_TEMPLATE_SPECIALIZATION (decl))
        {
          check_member_template (DECL_TI_TEMPLATE (decl));
          return DECL_TI_TEMPLATE (decl);
        }
      else
        return decl;
    } 
  else
    cp_error ("invalid member template declaration `%D'", decl);

  return error_mark_node;
}

/* Returns the template nesting level of the indicated class TYPE.
   
   For example, in:
     template <class T>
     struct A
     {
       template <class U>
       struct B {};
     };

   A<T>::B<U> has depth two, while A<T> has depth one.  
   Both A<T>::B<int> and A<int>::B<U> have depth one, if
   COUNT_SPECIALIZATIONS is 0 or if they are instantiations, not
   specializations.  

   This function is guaranteed to return 0 if passed NULL_TREE so
   that, for example, `template_class_depth (current_class_type)' is
   always safe.  */

static int 
template_class_depth_real (type, count_specializations)
     tree type;
     int count_specializations;
{
  int depth;

  for (depth = 0; 
       type && TREE_CODE (type) != NAMESPACE_DECL;
       type = (TREE_CODE (type) == FUNCTION_DECL) 
         ? DECL_REAL_CONTEXT (type) : TYPE_CONTEXT (type))
    {
      if (TREE_CODE (type) != FUNCTION_DECL)
        {
          if (CLASSTYPE_TEMPLATE_INFO (type)
              && PRIMARY_TEMPLATE_P (CLASSTYPE_TI_TEMPLATE (type))
              && ((count_specializations
                   && CLASSTYPE_TEMPLATE_SPECIALIZATION (type))
                  || uses_template_parms (CLASSTYPE_TI_ARGS (type))))
            ++depth;
        }
      else 
        {
          if (DECL_TEMPLATE_INFO (type)
              && PRIMARY_TEMPLATE_P (DECL_TI_TEMPLATE (type))
              && ((count_specializations
                   && DECL_TEMPLATE_SPECIALIZATION (type))
                  || uses_template_parms (DECL_TI_ARGS (type))))
            ++depth;
        }
    }

  return depth;
}

/* Returns the template nesting level of the indicated class TYPE.
   Like template_class_depth_real, but instantiations do not count in
   the depth.  */

int 
template_class_depth (type)
     tree type;
{
  return template_class_depth_real (type, /*count_specializations=*/0);
}

/* Returns 1 if processing DECL as part of do_pending_inlines
   needs us to push template parms.  */

static int
inline_needs_template_parms (decl)
     tree decl;
{
  if (! DECL_TEMPLATE_INFO (decl))
    return 0;

  return (TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (most_general_template (decl)))
          > (processing_template_decl + DECL_TEMPLATE_SPECIALIZATION (decl)));
}

/* Subroutine of maybe_begin_member_template_processing.
   Push the template parms in PARMS, starting from LEVELS steps into the
   chain, and ending at the beginning, since template parms are listed
   innermost first.  */

static void
push_inline_template_parms_recursive (parmlist, levels)
     tree parmlist;
     int levels;
{
  tree parms = TREE_VALUE (parmlist);
  int i;

  if (levels > 1)
    push_inline_template_parms_recursive (TREE_CHAIN (parmlist), levels - 1);

  ++processing_template_decl;
  current_template_parms
    = tree_cons (build_int_2 (0, processing_template_decl),
                 parms, current_template_parms);
  TEMPLATE_PARMS_FOR_INLINE (current_template_parms) = 1;

  pushlevel (0);
  for (i = 0; i < TREE_VEC_LENGTH (parms); ++i) 
    {
      tree parm = TREE_VALUE (TREE_VEC_ELT (parms, i));
      my_friendly_assert (TREE_CODE_CLASS (TREE_CODE (parm)) == 'd', 0);

      switch (TREE_CODE (parm))
        {
        case TYPE_DECL:
        case TEMPLATE_DECL:
          pushdecl (parm);
          break;

        case PARM_DECL:
          {
            /* Make a CONST_DECL as is done in process_template_parm.
               It is ugly that we recreate this here; the original
               version built in process_template_parm is no longer
               available.  */
            tree decl = build_decl (CONST_DECL, DECL_NAME (parm),
                                    TREE_TYPE (parm));
            SET_DECL_ARTIFICIAL (decl);
            DECL_INITIAL (decl) = DECL_INITIAL (parm);
            DECL_TEMPLATE_PARM_P (decl) = 1;
            pushdecl (decl);
          }
          break;

        default:
          my_friendly_abort (0);
        }
    }
}

/* Restore the template parameter context for a member template or
   a friend template defined in a class definition.  */

void
maybe_begin_member_template_processing (decl)
     tree decl;
{
  tree parms;
  int levels;

  if (! inline_needs_template_parms (decl))
    return;

  parms = DECL_TEMPLATE_PARMS (most_general_template (decl));

  levels = TMPL_PARMS_DEPTH (parms) - processing_template_decl;

  if (DECL_TEMPLATE_SPECIALIZATION (decl))
    {
      --levels;
      parms = TREE_CHAIN (parms);
    }

  push_inline_template_parms_recursive (parms, levels);
}

/* Undo the effects of begin_member_template_processing. */

void 
maybe_end_member_template_processing ()
{
  if (! processing_template_decl)
    return;

  while (current_template_parms
         && TEMPLATE_PARMS_FOR_INLINE (current_template_parms))
    {
      --processing_template_decl;
      current_template_parms = TREE_CHAIN (current_template_parms);
      poplevel (0, 0, 0);
    }
}

/* Returns non-zero iff T is a member template function.  We must be
   careful as in

     template <class T> class C { void f(); }

   Here, f is a template function, and a member, but not a member
   template.  This function does not concern itself with the origin of
   T, only its present state.  So if we have 

     template <class T> class C { template <class U> void f(U); }

   then neither C<int>::f<char> nor C<T>::f<double> is considered
   to be a member template.  But, `template <class U> void
   C<int>::f(U)' is considered a member template.  */

int
is_member_template (t)
     tree t;
{
  if (!DECL_FUNCTION_TEMPLATE_P (t))
    /* Anything that isn't a function or a template function is
       certainly not a member template.  */
    return 0;

  /* A local class can't have member templates.  */
  if (hack_decl_function_context (t))
    return 0;

  return (DECL_FUNCTION_MEMBER_P (DECL_TEMPLATE_RESULT (t))
          /* If there are more levels of template parameters than
             there are template classes surrounding the declaration,
             then we have a member template.  */
          && (TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (t)) > 
              template_class_depth (DECL_CLASS_CONTEXT (t))));
}

#if 0 /* UNUSED */
/* Returns non-zero iff T is a member template class.  See
   is_member_template for a description of what precisely constitutes
   a member template.  */

int
is_member_template_class (t)
     tree t;
{
  if (!DECL_CLASS_TEMPLATE_P (t))
    /* Anything that isn't a class template, is certainly not a member
       template.  */
    return 0;

  if (!DECL_CLASS_SCOPE_P (t))
    /* Anything whose context isn't a class type is surely not a
       member template.  */
    return 0;

  /* If there are more levels of template parameters than there are
     template classes surrounding the declaration, then we have a
     member template.  */
  return  (TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (t)) > 
           template_class_depth (DECL_CONTEXT (t)));
}
#endif

/* Return a new template argument vector which contains all of ARGS,
   but has as its innermost set of arguments the EXTRA_ARGS.  The
   resulting vector will be built on a temporary obstack, and so must
   be explicitly copied to the permanent obstack, if required.  */

static tree
add_to_template_args (args, extra_args)
     tree args;
     tree extra_args;
{
  tree new_args;
  int extra_depth;
  int i;
  int j;

  extra_depth = TMPL_ARGS_DEPTH (extra_args);
  new_args = make_temp_vec (TMPL_ARGS_DEPTH (args) + extra_depth);

  for (i = 1; i <= TMPL_ARGS_DEPTH (args); ++i)
    SET_TMPL_ARGS_LEVEL (new_args, i, TMPL_ARGS_LEVEL (args, i));

  for (j = 1; j <= extra_depth; ++j, ++i)
    SET_TMPL_ARGS_LEVEL (new_args, i, TMPL_ARGS_LEVEL (extra_args, j));
    
  return new_args;
}

/* Like add_to_template_args, but only the outermost ARGS are added to
   the EXTRA_ARGS.  In particular, all but TMPL_ARGS_DEPTH
   (EXTRA_ARGS) levels are added.  This function is used to combine
   the template arguments from a partial instantiation with the
   template arguments used to attain the full instantiation from the
   partial instantiation.  */

static tree
add_outermost_template_args (args, extra_args)
     tree args;
     tree extra_args;
{
  tree new_args;

  /* If there are more levels of EXTRA_ARGS than there are ARGS,
     something very fishy is going on.  */
  my_friendly_assert (TMPL_ARGS_DEPTH (args) >= TMPL_ARGS_DEPTH (extra_args),
                      0);

  /* If *all* the new arguments will be the EXTRA_ARGS, just return
     them.  */
  if (TMPL_ARGS_DEPTH (args) == TMPL_ARGS_DEPTH (extra_args))
    return extra_args;

  /* For the moment, we make ARGS look like it contains fewer levels.  */
  TREE_VEC_LENGTH (args) -= TMPL_ARGS_DEPTH (extra_args);
  
  new_args = add_to_template_args (args, extra_args);

  /* Now, we restore ARGS to its full dimensions.  */
  TREE_VEC_LENGTH (args) += TMPL_ARGS_DEPTH (extra_args);

  return new_args;
}

/* We've got a template header coming up; push to a new level for storing
   the parms.  */

void
begin_template_parm_list ()
{
  /* We use a non-tag-transparent scope here, which causes pushtag to
     put tags in this scope, rather than in the enclosing class or
     namespace scope.  This is the right thing, since we want
     TEMPLATE_DECLS, and not TYPE_DECLS for template classes.  For a
     global template class, push_template_decl handles putting the
     TEMPLATE_DECL into top-level scope.  For a nested template class,
     e.g.:

       template <class T> struct S1 {
         template <class T> struct S2 {}; 
       };

     pushtag contains special code to call pushdecl_with_scope on the
     TEMPLATE_DECL for S2.  */
  pushlevel (0);
  declare_pseudo_global_level ();
  ++processing_template_decl;
  ++processing_template_parmlist;
  note_template_header (0);
}

/* This routine is called when a specialization is declared.  If it is
   illegal to declare a specialization here, an error is reported.  */

static void
check_specialization_scope ()
{
  tree scope = current_scope ();

  /* [temp.expl.spec] 
     
     An explicit specialization shall be declared in the namespace of
     which the template is a member, or, for member templates, in the
     namespace of which the enclosing class or enclosing class
     template is a member.  An explicit specialization of a member
     function, member class or static data member of a class template
     shall be declared in the namespace of which the class template
     is a member.  */
  if (scope && TREE_CODE (scope) != NAMESPACE_DECL)
    cp_error ("explicit specialization in non-namespace scope `%D'",
              scope);

  /* [temp.expl.spec] 

     In an explicit specialization declaration for a member of a class
     template or a member template that appears in namespace scope,
     the member template and some of its enclosing class templates may
     remain unspecialized, except that the declaration shall not
     explicitly specialize a class member template if its enclosing
     class templates are not explicitly specialized as well.  */
  if (current_template_parms) 
    cp_error ("enclosing class templates are not explicitly specialized");
}

/* We've just seen template <>. */

void
begin_specialization ()
{
  note_template_header (1);
  check_specialization_scope ();
}

/* Called at then end of processing a declaration preceeded by
   template<>.  */

void 
end_specialization ()
{
  reset_specialization ();
}

/* Any template <>'s that we have seen thus far are not referring to a
   function specialization. */

void
reset_specialization ()
{
  processing_specialization = 0;
  template_header_count = 0;
}

/* We've just seen a template header.  If SPECIALIZATION is non-zero,
   it was of the form template <>.  */

static void 
note_template_header (specialization)
     int specialization;
{
  processing_specialization = specialization;
  template_header_count++;
}

/* We're beginning an explicit instantiation.  */

void
begin_explicit_instantiation ()
{
  ++processing_explicit_instantiation;
}


void
end_explicit_instantiation ()
{
  my_friendly_assert(processing_explicit_instantiation > 0, 0);
  --processing_explicit_instantiation;
}

/* The TYPE is being declared.  If it is a template type, that means it
   is a partial specialization.  Do appropriate error-checking.  */

void 
maybe_process_partial_specialization (type)
     tree type;
{
  if (IS_AGGR_TYPE (type) && CLASSTYPE_USE_TEMPLATE (type))
    {
      if (CLASSTYPE_IMPLICIT_INSTANTIATION (type)
          && TYPE_SIZE (type) == NULL_TREE)
        {
          if (current_namespace
              != decl_namespace_context (CLASSTYPE_TI_TEMPLATE (type)))
            {
              cp_pedwarn ("specializing `%#T' in different namespace", type);
              cp_pedwarn_at ("  from definition of `%#D'",
                             CLASSTYPE_TI_TEMPLATE (type));
            }
          SET_CLASSTYPE_TEMPLATE_SPECIALIZATION (type);
          if (processing_template_decl)
            push_template_decl (TYPE_MAIN_DECL (type));
        }
      else if (CLASSTYPE_TEMPLATE_INSTANTIATION (type))
        cp_error ("specialization of `%T' after instantiation", type);
    }
  else if (processing_specialization)
    cp_error ("explicit specialization of non-template `%T'", type);
}

/* Retrieve the specialization (in the sense of [temp.spec] - a
   specialization is either an instantiation or an explicit
   specialization) of TMPL for the given template ARGS.  If there is
   no such specialization, return NULL_TREE.  The ARGS are a vector of
   arguments, or a vector of vectors of arguments, in the case of
   templates with more than one level of parameters.  */
   
static tree
retrieve_specialization (tmpl, args)
     tree tmpl;
     tree args;
{
  tree s;

  my_friendly_assert (TREE_CODE (tmpl) == TEMPLATE_DECL, 0);

  /* There should be as many levels of arguments as there are
     levels of parameters.  */
  my_friendly_assert (TMPL_ARGS_DEPTH (args) 
                      == TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (tmpl)),
                      0);
                      
  for (s = DECL_TEMPLATE_SPECIALIZATIONS (tmpl);
       s != NULL_TREE;
       s = TREE_CHAIN (s))
    if (comp_template_args (TREE_PURPOSE (s), args))
      return TREE_VALUE (s);

  return NULL_TREE;
}

/* Returns non-zero iff DECL is a specialization of TMPL.  */

int
is_specialization_of (decl, tmpl)
     tree decl;
     tree tmpl;
{
  tree t;

  if (TREE_CODE (decl) == FUNCTION_DECL)
    {
      for (t = decl; 
           t != NULL_TREE;
           t = DECL_TEMPLATE_INFO (t) ? DECL_TI_TEMPLATE (t) : NULL_TREE)
        if (t == tmpl)
          return 1;
    }
  else 
    {
      my_friendly_assert (TREE_CODE (decl) == TYPE_DECL, 0);

      for (t = TREE_TYPE (decl);
           t != NULL_TREE;
           t = CLASSTYPE_USE_TEMPLATE (t)
             ? TREE_TYPE (CLASSTYPE_TI_TEMPLATE (t)) : NULL_TREE)
        if (same_type_p (TYPE_MAIN_VARIANT (t), 
                         TYPE_MAIN_VARIANT (TREE_TYPE (tmpl))))
          return 1;
    }  

  return 0;
}

/* Register the specialization SPEC as a specialization of TMPL with
   the indicated ARGS.  Returns SPEC, or an equivalent prior
   declaration, if available.  */

static tree
register_specialization (spec, tmpl, args)
     tree spec;
     tree tmpl;
     tree args;
{
  tree s;

  my_friendly_assert (TREE_CODE (tmpl) == TEMPLATE_DECL, 0);

  if (TREE_CODE (spec) == FUNCTION_DECL 
      && uses_template_parms (DECL_TI_ARGS (spec)))
    /* This is the FUNCTION_DECL for a partial instantiation.  Don't
       register it; we want the corresponding TEMPLATE_DECL instead.
       We use `uses_template_parms (DECL_TI_ARGS (spec))' rather than
       the more obvious `uses_template_parms (spec)' to avoid problems
       with default function arguments.  In particular, given
       something like this:

          template <class T> void f(T t1, T t = T())

       the default argument expression is not substituted for in an
       instantiation unless and until it is actually needed.  */
    return spec;
    
  /* There should be as many levels of arguments as there are
     levels of parameters.  */
  my_friendly_assert (TMPL_ARGS_DEPTH (args) 
                      == TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (tmpl)),
                      0);

  for (s = DECL_TEMPLATE_SPECIALIZATIONS (tmpl);
       s != NULL_TREE;
       s = TREE_CHAIN (s))
    if (comp_template_args (TREE_PURPOSE (s), args))
      {
        tree fn = TREE_VALUE (s);

        if (DECL_TEMPLATE_SPECIALIZATION (spec))
          {
            if (DECL_TEMPLATE_INSTANTIATION (fn))
              {
                if (TREE_USED (fn) 
                    || DECL_EXPLICIT_INSTANTIATION (fn))
                  {
                    cp_error ("specialization of %D after instantiation",
                              fn);
                    return spec;
                  }
                else
                  {
                    /* This situation should occur only if the first
                       specialization is an implicit instantiation,
                       the second is an explicit specialization, and
                       the implicit instantiation has not yet been
                       used.  That situation can occur if we have
                       implicitly instantiated a member function and
                       then specialized it later.

                       We can also wind up here if a friend
                       declaration that looked like an instantiation
                       turns out to be a specialization:

                         template <class T> void foo(T);
                         class S { friend void foo<>(int) };
                         template <> void foo(int);  

                       We transform the existing DECL in place so that
                       any pointers to it become pointers to the
                       updated declaration.  

                       If there was a definition for the template, but
                       not for the specialization, we want this to
                       look as if there is no definition, and vice
                       versa.  */
                    DECL_INITIAL (fn) = NULL_TREE;
                    duplicate_decls (spec, fn);

                    return fn;
                  }
              }
            else if (DECL_TEMPLATE_SPECIALIZATION (fn))
              {
                duplicate_decls (spec, fn);
                return fn;
              }
          }
      }

  DECL_TEMPLATE_SPECIALIZATIONS (tmpl)
     = perm_tree_cons (args, spec, DECL_TEMPLATE_SPECIALIZATIONS (tmpl));

  return spec;
}

/* Unregister the specialization SPEC as a specialization of TMPL.
   Returns nonzero if the SPEC was listed as a specialization of
   TMPL.  */

static int
unregister_specialization (spec, tmpl)
     tree spec;
     tree tmpl;
{
  tree* s;

  for (s = &DECL_TEMPLATE_SPECIALIZATIONS (tmpl);
       *s != NULL_TREE;
       s = &TREE_CHAIN (*s))
    if (TREE_VALUE (*s) == spec)
      {
        *s = TREE_CHAIN (*s);
        return 1;
      }

  return 0;
}

/* Print the list of candidate FNS in an error message.  */

void
print_candidates (fns)
     tree fns;
{
  tree fn;

  char* str = "candidates are:";

  for (fn = fns; fn != NULL_TREE; fn = TREE_CHAIN (fn))
    {
      tree f;

      for (f = TREE_VALUE (fn); f; f = OVL_NEXT (f))
        cp_error_at ("%s %+#D", str, OVL_CURRENT (f));
      str = "               ";
    }
}

/* Returns the template (one of the functions given by TEMPLATE_ID)
   which can be specialized to match the indicated DECL with the
   explicit template args given in TEMPLATE_ID.  The DECL may be
   NULL_TREE if none is available.  In that case, the functions in
   TEMPLATE_ID are non-members.

   If NEED_MEMBER_TEMPLATE is non-zero the function is known to be a
   specialization of a member template.

   The template args (those explicitly specified and those deduced)
   are output in a newly created vector *TARGS_OUT.

   If it is impossible to determine the result, an error message is
   issued.  The error_mark_node is returned to indicate failure.  */

static tree
determine_specialization (template_id, decl, targs_out, 
                          need_member_template)
     tree template_id;
     tree decl;
     tree* targs_out;
     int need_member_template;
{
  tree fn;
  tree fns;
  tree targs;
  tree explicit_targs;
  tree candidates = NULL_TREE;
  tree templates = NULL_TREE;

  *targs_out = NULL_TREE;

  if (template_id == error_mark_node)
    return error_mark_node;

  fns = TREE_OPERAND (template_id, 0);
  explicit_targs = TREE_OPERAND (template_id, 1);

  if (fns == error_mark_node)
    return error_mark_node;

  /* Check for baselinks. */
  if (TREE_CODE (fns) == TREE_LIST)
    fns = TREE_VALUE (fns);

  for (; fns; fns = OVL_NEXT (fns))
    {
      tree tmpl;

      fn = OVL_CURRENT (fns);

      if (TREE_CODE (fn) == TEMPLATE_DECL)
        /* DECL might be a specialization of FN.  */
        tmpl = fn;
      else if (need_member_template)
        /* FN is an ordinary member function, and we need a
           specialization of a member template.  */
        continue;
      else if (TREE_CODE (fn) != FUNCTION_DECL)
        /* We can get IDENTIFIER_NODEs here in certain erroneous
           cases.  */
        continue;
      else if (!DECL_FUNCTION_MEMBER_P (fn))
        /* This is just an ordinary non-member function.  Nothing can
           be a specialization of that.  */
        continue;
      else
        {
          tree decl_arg_types;

          /* This is an ordinary member function.  However, since
             we're here, we can assume it's enclosing class is a
             template class.  For example,
             
               template <typename T> struct S { void f(); };
               template <> void S<int>::f() {}

             Here, S<int>::f is a non-template, but S<int> is a
             template class.  If FN has the same type as DECL, we
             might be in business.  */
          if (!same_type_p (TREE_TYPE (TREE_TYPE (decl)),
                            TREE_TYPE (TREE_TYPE (fn))))
            /* The return types differ.  */
            continue;

          /* Adjust the type of DECL in case FN is a static member.  */
          decl_arg_types = TYPE_ARG_TYPES (TREE_TYPE (decl));
          if (DECL_STATIC_FUNCTION_P (fn) 
              && DECL_NONSTATIC_MEMBER_FUNCTION_P (decl))
            decl_arg_types = TREE_CHAIN (decl_arg_types);

          if (compparms (TYPE_ARG_TYPES (TREE_TYPE (fn)), 
                         decl_arg_types))
            /* They match!  */
            candidates = tree_cons (NULL_TREE, fn, candidates);

          continue;
        }

      /* See whether this function might be a specialization of this
         template.  */
      targs = get_bindings (tmpl, decl, explicit_targs);

      if (!targs)
        /* We cannot deduce template arguments that when used to
           specialize TMPL will produce DECL.  */
        continue;

      /* Save this template, and the arguments deduced.  */
      templates = scratch_tree_cons (targs, tmpl, templates);
    }

  if (templates && TREE_CHAIN (templates))
    {
      /* We have:
         
           [temp.expl.spec]

           It is possible for a specialization with a given function
           signature to be instantiated from more than one function
           template.  In such cases, explicit specification of the
           template arguments must be used to uniquely identify the
           function template specialization being specialized.

         Note that here, there's no suggestion that we're supposed to
         determine which of the candidate templates is most
         specialized.  However, we, also have:

           [temp.func.order]

           Partial ordering of overloaded function template
           declarations is used in the following contexts to select
           the function template to which a function template
           specialization refers: 

           -- when an explicit specialization refers to a function
              template. 

         So, we do use the partial ordering rules, at least for now.
         This extension can only serve to make illegal programs legal,
         so it's safe.  And, there is strong anecdotal evidence that
         the committee intended the partial ordering rules to apply;
         the EDG front-end has that behavior, and John Spicer claims
         that the committee simply forgot to delete the wording in
         [temp.expl.spec].  */
     tree tmpl = most_specialized (templates, decl, explicit_targs);
     if (tmpl && tmpl != error_mark_node)
       {
         targs = get_bindings (tmpl, decl, explicit_targs);
         templates = scratch_tree_cons (targs, tmpl, NULL_TREE);
       }
    }

  if (templates == NULL_TREE && candidates == NULL_TREE)
    {
      cp_error_at ("template-id `%D' for `%+D' does not match any template declaration",
                   template_id, decl);
      return error_mark_node;
    }
  else if ((templates && TREE_CHAIN (templates))
           || (candidates && TREE_CHAIN (candidates))
           || (templates && candidates))
    {
      cp_error_at ("ambiguous template specialization `%D' for `%+D'",
                   template_id, decl);
      chainon (candidates, templates);
      print_candidates (candidates);
      return error_mark_node;
    }

  /* We have one, and exactly one, match. */
  if (candidates)
    {
      /* It was a specialization of an ordinary member function in a
         template class.  */
      *targs_out = copy_node (DECL_TI_ARGS (TREE_VALUE (candidates)));
      return DECL_TI_TEMPLATE (TREE_VALUE (candidates));
    }

  /* It was a specialization of a template.  */
  targs = DECL_TI_ARGS (DECL_RESULT (TREE_VALUE (templates)));
  if (TMPL_ARGS_HAVE_MULTIPLE_LEVELS (targs))
    {
      *targs_out = copy_node (targs);
      SET_TMPL_ARGS_LEVEL (*targs_out, 
                           TMPL_ARGS_DEPTH (*targs_out),
                           TREE_PURPOSE (templates));
    }
  else
    *targs_out = TREE_PURPOSE (templates);
  return TREE_VALUE (templates);
}
      
/* Check to see if the function just declared, as indicated in
   DECLARATOR, and in DECL, is a specialization of a function
   template.  We may also discover that the declaration is an explicit
   instantiation at this point.

   Returns DECL, or an equivalent declaration that should be used
   instead if all goes well.  Issues an error message if something is
   amiss.  Returns error_mark_node if the error is not easily
   recoverable.
   
   FLAGS is a bitmask consisting of the following flags: 

   2: The function has a definition.
   4: The function is a friend.

   The TEMPLATE_COUNT is the number of references to qualifying
   template classes that appeared in the name of the function.  For
   example, in

     template <class T> struct S { void f(); };
     void S<int>::f();
     
   the TEMPLATE_COUNT would be 1.  However, explicitly specialized
   classes are not counted in the TEMPLATE_COUNT, so that in

     template <class T> struct S {};
     template <> struct S<int> { void f(); }
     template <> void S<int>::f();

   the TEMPLATE_COUNT would be 0.  (Note that this declaration is
   illegal; there should be no template <>.)

   If the function is a specialization, it is marked as such via
   DECL_TEMPLATE_SPECIALIZATION.  Furthermore, its DECL_TEMPLATE_INFO
   is set up correctly, and it is added to the list of specializations 
   for that template.  */

tree
check_explicit_specialization (declarator, decl, template_count, flags)
     tree declarator;
     tree decl;
     int template_count;
     int flags;
{
  int have_def = flags & 2;
  int is_friend = flags & 4;
  int specialization = 0;
  int explicit_instantiation = 0;
  int member_specialization = 0;

  tree ctype = DECL_CLASS_CONTEXT (decl);
  tree dname = DECL_NAME (decl);

  if (processing_specialization) 
    {
      /* The last template header was of the form template <>.  */
          
      if (template_header_count > template_count) 
        {
          /* There were more template headers than qualifying template
             classes.  */
          if (template_header_count - template_count > 1)
            /* There shouldn't be that many template parameter lists.
               There can be at most one parameter list for every
               qualifying class, plus one for the function itself.  */
            cp_error ("too many template parameter lists in declaration of `%D'", decl);

          SET_DECL_TEMPLATE_SPECIALIZATION (decl);
          if (ctype)
            member_specialization = 1;
          else
            specialization = 1;
        }
      else if (template_header_count == template_count)
        {
          /* The counts are equal.  So, this might be a
             specialization, but it is not a specialization of a
             member template.  It might be something like
                 
             template <class T> struct S { 
             void f(int i); 
             };
             template <>
             void S<int>::f(int i) {}  */
          specialization = 1;
          SET_DECL_TEMPLATE_SPECIALIZATION (decl);
        }
      else 
        {
          /* This cannot be an explicit specialization.  There are not
             enough headers for all of the qualifying classes.  For
             example, we might have:
             
             template <>
             void S<int>::T<char>::f();

             But, we're missing another template <>.  */
          cp_error("too few template parameter lists in declaration of `%D'", decl);
          return decl;
        } 
    }
  else if (processing_explicit_instantiation)
    {
      if (template_header_count)
        cp_error ("template parameter list used in explicit instantiation");
          
      if (have_def)
        cp_error ("definition provided for explicit instantiation");

      explicit_instantiation = 1;
    }
  else if (ctype != NULL_TREE
           && !TYPE_BEING_DEFINED (ctype)
           && CLASSTYPE_TEMPLATE_INSTANTIATION (ctype)
           && !is_friend)
    {
      /* This case catches outdated code that looks like this:

         template <class T> struct S { void f(); };
         void S<int>::f() {} // Missing template <>

         We disable this check when the type is being defined to
         avoid complaining about default compiler-generated
         constructors, destructors, and assignment operators.
         Since the type is an instantiation, not a specialization,
         these are the only functions that can be defined before
         the class is complete.  */

          /* If they said
               template <class T> void S<int>::f() {}
             that's bogus.  */
      if (template_header_count)
        {
          cp_error ("template parameters specified in specialization");
          return decl;
        }

      if (pedantic)
        cp_pedwarn
          ("explicit specialization not preceded by `template <>'");
      specialization = 1;
      SET_DECL_TEMPLATE_SPECIALIZATION (decl);
    }
  else if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
    {
      if (is_friend)
        /* This could be something like:

           template <class T> void f(T);
           class S { friend void f<>(int); }  */
        specialization = 1;
      else
        {
          /* This case handles bogus declarations like template <>
             template <class T> void f<int>(); */

          cp_error ("template-id `%D' in declaration of primary template",
                    declarator);
          return decl;
        }
    }

  if (specialization || member_specialization)
    {
      tree t = TYPE_ARG_TYPES (TREE_TYPE (decl));
      for (; t; t = TREE_CHAIN (t))
        if (TREE_PURPOSE (t))
          {
            cp_pedwarn
              ("default argument specified in explicit specialization");
            break;
          }
      if (current_lang_name == lang_name_c)
        cp_error ("template specialization with C linkage");
    }

  if (specialization || member_specialization || explicit_instantiation)
    {
      tree gen_tmpl;
      tree tmpl = NULL_TREE;
      tree targs = NULL_TREE;

      /* Make sure that the declarator is a TEMPLATE_ID_EXPR.  */
      if (TREE_CODE (declarator) != TEMPLATE_ID_EXPR)
        {
          tree fns;

          my_friendly_assert (TREE_CODE (declarator) == IDENTIFIER_NODE, 
                              0);
          if (!ctype)
            fns = IDENTIFIER_NAMESPACE_VALUE (dname);
          else
            fns = dname;

          declarator = 
            lookup_template_function (fns, NULL_TREE);
        }

      if (declarator == error_mark_node)
        return error_mark_node;

      if (TREE_CODE (TREE_OPERAND (declarator, 0)) == LOOKUP_EXPR)
        {
          /* A friend declaration.  We can't do much, because we don't
           know what this resolves to, yet.  */
          my_friendly_assert (is_friend != 0, 0);
          my_friendly_assert (!explicit_instantiation, 0);
          SET_DECL_IMPLICIT_INSTANTIATION (decl);
          return decl;
        } 

      if (ctype != NULL_TREE && TYPE_BEING_DEFINED (ctype))
        {
          if (!explicit_instantiation)
            /* A specialization in class scope.  This is illegal,
               but the error will already have been flagged by
               check_specialization_scope.  */
            return error_mark_node;
          else
            {
              /* It's not legal to write an explicit instantiation in
                 class scope, e.g.:

                   class C { template void f(); }

                   This case is caught by the parser.  However, on
                   something like:
               
                   template class C { void f(); };

                   (which is illegal) we can get here.  The error will be
                   issued later.  */
              ;
            }

          return decl;
        }
      else if (ctype != NULL_TREE 
               && (TREE_CODE (TREE_OPERAND (declarator, 0)) ==
                   IDENTIFIER_NODE))
        {
          /* Find the list of functions in ctype that have the same
             name as the declared function.  */
          tree name = TREE_OPERAND (declarator, 0);
          tree fns = NULL_TREE;
          int idx;

          if (name == constructor_name (ctype) 
              || name == constructor_name_full (ctype))
            {
              int is_constructor = DECL_CONSTRUCTOR_P (decl);
              
              if (is_constructor ? !TYPE_HAS_CONSTRUCTOR (ctype)
                  : !TYPE_HAS_DESTRUCTOR (ctype))
                {
                  /* From [temp.expl.spec]:
                       
                     If such an explicit specialization for the member
                     of a class template names an implicitly-declared
                     special member function (clause _special_), the
                     program is ill-formed.  

                     Similar language is found in [temp.explicit].  */
                  cp_error ("specialization of implicitly-declared special member function");
                  return error_mark_node;
                }

              name = is_constructor ? ctor_identifier : dtor_identifier;
            }

          if (!IDENTIFIER_TYPENAME_P (name))
            {
              idx = lookup_fnfields_1 (ctype, name);
              if (idx >= 0)
                fns = TREE_VEC_ELT (CLASSTYPE_METHOD_VEC (ctype), idx);
            }
          else
            {
              tree methods;

              /* For a type-conversion operator, we cannot do a
                 name-based lookup.  We might be looking for `operator
                 int' which will be a specialization of `operator T'.
                 So, we find *all* the conversion operators, and then
                 select from them.  */
              fns = NULL_TREE;

              methods = CLASSTYPE_METHOD_VEC (ctype);
              if (methods)
                for (idx = 2; idx < TREE_VEC_LENGTH (methods); ++idx) 
                  {
                    tree ovl = TREE_VEC_ELT (methods, idx);

                    if (!ovl || !DECL_CONV_FN_P (OVL_CURRENT (ovl)))
                      /* There are no more conversion functions.  */
                      break;

                    /* Glue all these conversion functions together
                       with those we already have.  */
                    for (; ovl; ovl = OVL_NEXT (ovl))
                      fns = ovl_cons (OVL_CURRENT (ovl), fns);
                  }
            }
              
          if (fns == NULL_TREE) 
            {
              cp_error ("no member function `%s' declared in `%T'",
                        IDENTIFIER_POINTER (name),
                        ctype);
              return error_mark_node;
            }
          else
            TREE_OPERAND (declarator, 0) = fns;
        }
      
      /* Figure out what exactly is being specialized at this point.
         Note that for an explicit instantiation, even one for a
         member function, we cannot tell apriori whether the
         instantiation is for a member template, or just a member
         function of a template class.  Even if a member template is
         being instantiated, the member template arguments may be
         elided if they can be deduced from the rest of the
         declaration.  */
      tmpl = determine_specialization (declarator, decl,
                                       &targs, 
                                       member_specialization);
            
      if (!tmpl || tmpl == error_mark_node)
        /* We couldn't figure out what this declaration was
           specializing.  */
        return error_mark_node;
      else
        {
          gen_tmpl = most_general_template (tmpl);

          if (explicit_instantiation)
            {
              /* We don't set DECL_EXPLICIT_INSTANTIATION here; that
                 is done by do_decl_instantiation later.  */
              decl = instantiate_template (tmpl, innermost_args (targs));
              return decl;
            }
          
          /* If we though that the DECL was a member function, but it
             turns out to be specializing a static member function,
             make DECL a static member function as well.  */
          if (DECL_STATIC_FUNCTION_P (tmpl)
              && DECL_NONSTATIC_MEMBER_FUNCTION_P (decl))
            {
              revert_static_member_fn (&decl, 0, 0);
              last_function_parms = TREE_CHAIN (last_function_parms);
            }

          /* Set up the DECL_TEMPLATE_INFO for DECL.  */
          DECL_TEMPLATE_INFO (decl) 
            = perm_tree_cons (tmpl, targs, NULL_TREE);

          /* Mangle the function name appropriately.  Note that we do
             not mangle specializations of non-template member
             functions of template classes, e.g. with

               template <class T> struct S { void f(); }

             and given the specialization 

               template <> void S<int>::f() {}

             we do not mangle S<int>::f() here.  That's because it's
             just an ordinary member function and doesn't need special
             treatment.  We do this here so that the ordinary,
             non-template, name-mangling algorith will not be used
             later.  */
          if ((is_member_template (tmpl) || ctype == NULL_TREE)
              && name_mangling_version >= 1)
            set_mangled_name_for_template_decl (decl);

          if (is_friend && !have_def)
            /* This is not really a declaration of a specialization.
               It's just the name of an instantiation.  But, it's not
               a request for an instantiation, either.  */
            SET_DECL_IMPLICIT_INSTANTIATION (decl);

          /* Register this specialization so that we can find it
             again.  */
          decl = register_specialization (decl, gen_tmpl, targs);
        }
    }
  
  return decl;
}

/* TYPE is being declared.  Verify that the use of template headers
   and such is reasonable.  Issue error messages if not.  */

void
maybe_check_template_type (type)
     tree type;
{
  if (template_header_count)
    {
      /* We are in the scope of some `template <...>' header.  */

      int context_depth 
        = template_class_depth_real (TYPE_CONTEXT (type),
                                     /*count_specializations=*/1);

      if (template_header_count <= context_depth)
        /* This is OK; the template headers are for the context.  We
           are actually too lenient here; like
           check_explicit_specialization we should consider the number
           of template types included in the actual declaration.  For
           example, 

             template <class T> struct S {
               template <class U> template <class V>
               struct I {};
             }; 

           is illegal, but:

             template <class T> struct S {
               template <class U> struct I;
             }; 

             template <class T> template <class U.
             struct S<T>::I {};

           is not.  */
        ; 
      else if (template_header_count > context_depth + 1)
        /* There are two many template parameter lists.  */
        cp_error ("too many template parameter lists in declaration of `%T'", type); 
    }
}

/* Returns 1 iff PARMS1 and PARMS2 are identical sets of template
   parameters.  These are represented in the same format used for
   DECL_TEMPLATE_PARMS.  */

int comp_template_parms (parms1, parms2)
     tree parms1;
     tree parms2;
{
  tree p1;
  tree p2;

  if (parms1 == parms2)
    return 1;

  for (p1 = parms1, p2 = parms2; 
       p1 != NULL_TREE && p2 != NULL_TREE;
       p1 = TREE_CHAIN (p1), p2 = TREE_CHAIN (p2))
    {
      tree t1 = TREE_VALUE (p1);
      tree t2 = TREE_VALUE (p2);
      int i;

      my_friendly_assert (TREE_CODE (t1) == TREE_VEC, 0);
      my_friendly_assert (TREE_CODE (t2) == TREE_VEC, 0);

      if (TREE_VEC_LENGTH (t1) != TREE_VEC_LENGTH (t2))
        return 0;

      for (i = 0; i < TREE_VEC_LENGTH (t2); ++i) 
        {
          tree parm1 = TREE_VALUE (TREE_VEC_ELT (t1, i));
          tree parm2 = TREE_VALUE (TREE_VEC_ELT (t2, i));

          if (TREE_CODE (parm1) != TREE_CODE (parm2))
            return 0;

          if (TREE_CODE (parm1) == TEMPLATE_TYPE_PARM)
            continue;
          else if (!same_type_p (TREE_TYPE (parm1), TREE_TYPE (parm2)))
            return 0;
        }
    }

  if ((p1 != NULL_TREE) != (p2 != NULL_TREE))
    /* One set of parameters has more parameters lists than the
       other.  */
    return 0;

  return 1;
}

/* Complain if DECL shadows a template parameter.

   [temp.local]: A template-parameter shall not be redeclared within its
   scope (including nested scopes).  */

void
check_template_shadow (decl)
     tree decl;
{
  tree olddecl = IDENTIFIER_VALUE (DECL_NAME (decl));

  if (current_template_parms && olddecl)
    {
      /* We check for decl != olddecl to avoid bogus errors for using a
         name inside a class.  We check TPFI to avoid duplicate errors for
         inline member templates.  */
      if (decl != olddecl && DECL_TEMPLATE_PARM_P (olddecl)
          && ! TEMPLATE_PARMS_FOR_INLINE (current_template_parms))
        {
          cp_error_at ("declaration of `%#D'", decl);
          cp_error_at (" shadows template parm `%#D'", olddecl);
        }
    }
}

/* Return a new TEMPLATE_PARM_INDEX with the indicated INDEX, LEVEL,
   ORIG_LEVEL, DECL, and TYPE.  */

static tree
build_template_parm_index (index, level, orig_level, decl, type)
     int index;
     int level;
     int orig_level;
     tree decl;
     tree type;
{
  tree t = make_node (TEMPLATE_PARM_INDEX);
  TEMPLATE_PARM_IDX (t) = index;
  TEMPLATE_PARM_LEVEL (t) = level;
  TEMPLATE_PARM_ORIG_LEVEL (t) = orig_level;
  TEMPLATE_PARM_DECL (t) = decl;
  TREE_TYPE (t) = type;

  return t;
}

/* Return a TEMPLATE_PARM_INDEX, similar to INDEX, but whose
   TEMPLATE_PARM_LEVEL has been decreased by LEVELS.  If such a
   TEMPLATE_PARM_INDEX already exists, it is returned; otherwise, a
   new one is created.  */

static tree 
reduce_template_parm_level (index, type, levels)
     tree index;
     tree type;
     int levels;
{
  if (TEMPLATE_PARM_DESCENDANTS (index) == NULL_TREE
      || (TEMPLATE_PARM_LEVEL (TEMPLATE_PARM_DESCENDANTS (index))
          != TEMPLATE_PARM_LEVEL (index) - levels))
    {
      tree decl 
        = build_decl (TREE_CODE (TEMPLATE_PARM_DECL (index)),
                      DECL_NAME (TEMPLATE_PARM_DECL (index)),
                      type);
      tree t
        = build_template_parm_index (TEMPLATE_PARM_IDX (index),
                                     TEMPLATE_PARM_LEVEL (index) - levels,
                                     TEMPLATE_PARM_ORIG_LEVEL (index),
                                     decl, type);
      TEMPLATE_PARM_DESCENDANTS (index) = t;

      /* Template template parameters need this.  */
      DECL_TEMPLATE_PARMS (decl)
        = DECL_TEMPLATE_PARMS (TEMPLATE_PARM_DECL (index));
    }

  return TEMPLATE_PARM_DESCENDANTS (index);
}

/* Process information from new template parameter NEXT and append it to the
   LIST being built.  */

tree
process_template_parm (list, next)
     tree list, next;
{
  tree parm;
  tree decl = 0;
  tree defval;
  int is_type, idx;

  parm = next;
  my_friendly_assert (TREE_CODE (parm) == TREE_LIST, 259);
  defval = TREE_PURPOSE (parm);
  parm = TREE_VALUE (parm);
  is_type = TREE_PURPOSE (parm) == class_type_node;

  if (list)
    {
      tree p = TREE_VALUE (tree_last (list));

      if (TREE_CODE (p) == TYPE_DECL)
        idx = TEMPLATE_TYPE_IDX (TREE_TYPE (p));
      else if (TREE_CODE (p) == TEMPLATE_DECL)
        idx = TEMPLATE_TYPE_IDX (TREE_TYPE (DECL_TEMPLATE_RESULT (p)));
      else
        idx = TEMPLATE_PARM_IDX (DECL_INITIAL (p));
      ++idx;
    }
  else
    idx = 0;

  if (!is_type)
    {
      my_friendly_assert (TREE_CODE (TREE_PURPOSE (parm)) == TREE_LIST, 260);
      /* is a const-param */
      parm = grokdeclarator (TREE_VALUE (parm), TREE_PURPOSE (parm),
                             PARM, 0, NULL_TREE);

      /* [temp.param]

         The top-level cv-qualifiers on the template-parameter are
         ignored when determining its type.  */
      TREE_TYPE (parm) = TYPE_MAIN_VARIANT (TREE_TYPE (parm));

      /* A template parameter is not modifiable.  */
      TREE_READONLY (parm) = 1;
      if (IS_AGGR_TYPE (TREE_TYPE (parm))
          && TREE_CODE (TREE_TYPE (parm)) != TEMPLATE_TYPE_PARM
          && TREE_CODE (TREE_TYPE (parm)) != TYPENAME_TYPE)
        {
          cp_error ("`%#T' is not a valid type for a template constant parameter",
                    TREE_TYPE (parm));
          if (DECL_NAME (parm) == NULL_TREE)
            error ("  a template type parameter must begin with `class' or `typename'");
          TREE_TYPE (parm) = void_type_node;
        }
      else if (pedantic
               && (TREE_CODE (TREE_TYPE (parm)) == REAL_TYPE
                   || TREE_CODE (TREE_TYPE (parm)) == COMPLEX_TYPE))
        cp_pedwarn ("`%T' is not a valid type for a template constant parameter",
                    TREE_TYPE (parm));
      if (TREE_PERMANENT (parm) == 0)
        {
          parm = copy_node (parm);
          TREE_PERMANENT (parm) = 1;
        }
      decl = build_decl (CONST_DECL, DECL_NAME (parm), TREE_TYPE (parm));
      DECL_INITIAL (parm) = DECL_INITIAL (decl) 
        = build_template_parm_index (idx, processing_template_decl,
                                     processing_template_decl,
                                     decl, TREE_TYPE (parm));
    }
  else
    {
      tree t;
      parm = TREE_VALUE (parm);
      
      if (parm && TREE_CODE (parm) == TEMPLATE_DECL)
        {
          t = make_lang_type (TEMPLATE_TEMPLATE_PARM);
          /* This is for distinguishing between real templates and template 
             template parameters */
          TREE_TYPE (parm) = t;
          TREE_TYPE (DECL_TEMPLATE_RESULT (parm)) = t;
          decl = parm;
        }
      else
        {
          t = make_lang_type (TEMPLATE_TYPE_PARM);
          /* parm is either IDENTIFIER_NODE or NULL_TREE */
          decl = build_decl (TYPE_DECL, parm, t);
        }
        
      TYPE_NAME (t) = decl;
      TYPE_STUB_DECL (t) = decl;
      parm = decl;
      TEMPLATE_TYPE_PARM_INDEX (t)
        = build_template_parm_index (idx, processing_template_decl, 
                                     processing_template_decl,
                                     decl, TREE_TYPE (parm));
    }
  SET_DECL_ARTIFICIAL (decl);
  DECL_TEMPLATE_PARM_P (decl) = 1;
  pushdecl (decl);
  parm = build_tree_list (defval, parm);
  return chainon (list, parm);
}

/* The end of a template parameter list has been reached.  Process the
   tree list into a parameter vector, converting each parameter into a more
   useful form.  Type parameters are saved as IDENTIFIER_NODEs, and others
   as PARM_DECLs.  */

tree
end_template_parm_list (parms)
     tree parms;
{
  int nparms;
  tree parm;
  tree saved_parmlist = make_tree_vec (list_length (parms));

  current_template_parms
    = tree_cons (build_int_2 (0, processing_template_decl),
                 saved_parmlist, current_template_parms);

  for (parm = parms, nparms = 0; parm; parm = TREE_CHAIN (parm), nparms++)
    TREE_VEC_ELT (saved_parmlist, nparms) = parm;

  --processing_template_parmlist;

  return saved_parmlist;
}

/* end_template_decl is called after a template declaration is seen.  */

void
end_template_decl ()
{
  reset_specialization ();

  if (! processing_template_decl)
    return;

  /* This matches the pushlevel in begin_template_parm_list.  */
  poplevel (0, 0, 0);

  --processing_template_decl;
  current_template_parms = TREE_CHAIN (current_template_parms);
  (void) get_pending_sizes ();  /* Why? */
}

/* Given a template argument vector containing the template PARMS.
   The innermost PARMS are given first.  */

tree
current_template_args ()
{
  tree header;
  tree args = NULL_TREE;
  int length = TMPL_PARMS_DEPTH (current_template_parms);
  int l = length;

  /* If there is only one level of template parameters, we do not
     create a TREE_VEC of TREE_VECs.  Instead, we return a single
     TREE_VEC containing the arguments.  */
  if (length > 1)
    args = make_tree_vec (length);

  for (header = current_template_parms; header; header = TREE_CHAIN (header))
    {
      tree a = copy_node (TREE_VALUE (header));
      int i;

      TREE_TYPE (a) = NULL_TREE;
      for (i = TREE_VEC_LENGTH (a) - 1; i >= 0; --i)
        {
          tree t = TREE_VEC_ELT (a, i);

          /* T will be a list if we are called from within a
             begin/end_template_parm_list pair, but a vector directly
             if within a begin/end_member_template_processing pair.  */
          if (TREE_CODE (t) == TREE_LIST) 
            {
              t = TREE_VALUE (t);
              
              if (TREE_CODE (t) == TYPE_DECL 
                  || TREE_CODE (t) == TEMPLATE_DECL)
                t = TREE_TYPE (t);
              else
                t = DECL_INITIAL (t);
              TREE_VEC_ELT (a, i) = t;
            }
        }

      if (length > 1)
        TREE_VEC_ELT (args, --l) = a;
      else
        args = a;
    }

  return args;
}

/* Return a TEMPLATE_DECL corresponding to DECL, using the indicated
   template PARMS.  Used by push_template_decl below.  */

static tree
build_template_decl (decl, parms)
     tree decl;
     tree parms;
{
  tree tmpl = build_lang_decl (TEMPLATE_DECL, DECL_NAME (decl), NULL_TREE);
  DECL_TEMPLATE_PARMS (tmpl) = parms;
  DECL_CONTEXT (tmpl) = DECL_CONTEXT (decl);
  if (DECL_LANG_SPECIFIC (decl))
    {
      DECL_CLASS_CONTEXT (tmpl) = DECL_CLASS_CONTEXT (decl);
      DECL_STATIC_FUNCTION_P (tmpl) = 
        DECL_STATIC_FUNCTION_P (decl);
    }

  return tmpl;
}

struct template_parm_data
{
  /* The level of the template parameters we are currently
     processing.  */
  int level;

  /* The index of the specialization argument we are currently
     processing.  */
  int current_arg;

  /* An array whose size is the number of template parameters.  The
     elements are non-zero if the parameter has been used in any one
     of the arguments processed so far.  */
  int* parms;

  /* An array whose size is the number of template arguments.  The
     elements are non-zero if the argument makes use of template
     parameters of this level.  */
  int* arg_uses_template_parms;
};

/* Subroutine of push_template_decl used to see if each template
   parameter in a partial specialization is used in the explicit
   argument list.  If T is of the LEVEL given in DATA (which is
   treated as a template_parm_data*), then DATA->PARMS is marked
   appropriately.  */

static int
mark_template_parm (t, data)
     tree t;
     void* data;
{
  int level;
  int idx;
  struct template_parm_data* tpd = (struct template_parm_data*) data;

  if (TREE_CODE (t) == TEMPLATE_PARM_INDEX)
    {
      level = TEMPLATE_PARM_LEVEL (t);
      idx = TEMPLATE_PARM_IDX (t);
    }
  else
    {
      level = TEMPLATE_TYPE_LEVEL (t);
      idx = TEMPLATE_TYPE_IDX (t);
    }

  if (level == tpd->level)
    {
      tpd->parms[idx] = 1;
      tpd->arg_uses_template_parms[tpd->current_arg] = 1;
    }

  /* Return zero so that for_each_template_parm will continue the
     traversal of the tree; we want to mark *every* template parm.  */
  return 0;
}

/* Process the partial specialization DECL.  */

static tree
process_partial_specialization (decl)
     tree decl;
{
  tree type = TREE_TYPE (decl);
  tree maintmpl = CLASSTYPE_TI_TEMPLATE (type);
  tree specargs = CLASSTYPE_TI_ARGS (type);
  tree inner_args = innermost_args (specargs);
  tree inner_parms = INNERMOST_TEMPLATE_PARMS (current_template_parms);
  tree main_inner_parms = DECL_INNERMOST_TEMPLATE_PARMS (maintmpl);
  int nargs = TREE_VEC_LENGTH (inner_args);
  int ntparms = TREE_VEC_LENGTH (inner_parms);
  int  i;
  int did_error_intro = 0;
  struct template_parm_data tpd;
  struct template_parm_data tpd2;

  /* We check that each of the template parameters given in the
     partial specialization is used in the argument list to the
     specialization.  For example:

       template <class T> struct S;
       template <class T> struct S<T*>;

     The second declaration is OK because `T*' uses the template
     parameter T, whereas

       template <class T> struct S<int>;

     is no good.  Even trickier is:

       template <class T>
       struct S1
       {
          template <class U>
          struct S2;
          template <class U>
          struct S2<T>;
       };

     The S2<T> declaration is actually illegal; it is a
     full-specialization.  Of course, 

          template <class U>
          struct S2<T (*)(U)>;

     or some such would have been OK.  */
  tpd.level = TMPL_PARMS_DEPTH (current_template_parms);
  tpd.parms = alloca (sizeof (int) * ntparms);
  bzero ((PTR) tpd.parms, sizeof (int) * ntparms);

  tpd.arg_uses_template_parms = alloca (sizeof (int) * nargs);
  bzero ((PTR) tpd.arg_uses_template_parms, sizeof (int) * nargs);
  for (i = 0; i < nargs; ++i)
    {
      tpd.current_arg = i;
      for_each_template_parm (TREE_VEC_ELT (inner_args, i),
                              &mark_template_parm,
                              &tpd);
    }
  for (i = 0; i < ntparms; ++i)
    if (tpd.parms[i] == 0)
      {
        /* One of the template parms was not used in the
           specialization.  */
        if (!did_error_intro)
          {
            cp_error ("template parameters not used in partial specialization:");
            did_error_intro = 1;
          }

        cp_error ("        `%D'", 
                  TREE_VALUE (TREE_VEC_ELT (inner_parms, i)));
      }

  /* [temp.class.spec]

     The argument list of the specialization shall not be identical to
     the implicit argument list of the primary template.  */
  if (comp_template_args (inner_args, 
                          innermost_args (CLASSTYPE_TI_ARGS (TREE_TYPE
                                                             (maintmpl)))))
    cp_error ("partial specialization `%T' does not specialize any template arguments", type);

  /* [temp.class.spec]

     A partially specialized non-type argument expression shall not
     involve template parameters of the partial specialization except
     when the argument expression is a simple identifier.

     The type of a template parameter corresponding to a specialized
     non-type argument shall not be dependent on a parameter of the
     specialization.  */
  my_friendly_assert (nargs == DECL_NTPARMS (maintmpl), 0);
  tpd2.parms = 0;
  for (i = 0; i < nargs; ++i)
    {
      tree arg = TREE_VEC_ELT (inner_args, i);
      if (/* These first two lines are the `non-type' bit.  */
          TREE_CODE_CLASS (TREE_CODE (arg)) != 't'
          && TREE_CODE (arg) != TEMPLATE_DECL
          /* This next line is the `argument expression is not just a
             simple identifier' condition and also the `specialized
             non-type argument' bit.  */
          && TREE_CODE (arg) != TEMPLATE_PARM_INDEX)
        {
          if (tpd.arg_uses_template_parms[i])
            cp_error ("template argument `%E' involves template parameter(s)", arg);
          else 
            {
              /* Look at the corresponding template parameter,
                 marking which template parameters its type depends
                 upon.  */
              tree type = 
                TREE_TYPE (TREE_VALUE (TREE_VEC_ELT (main_inner_parms, 
                                                     i)));

              if (!tpd2.parms)
                {
                  /* We haven't yet initialized TPD2.  Do so now.  */
                  tpd2.arg_uses_template_parms 
                    =  (int*) alloca (sizeof (int) * nargs);
                  /* The number of parameters here is the number in the
                     main template, which, as checked in the assertion
                     above, is NARGS.  */
                  tpd2.parms = (int*) alloca (sizeof (int) * nargs);
                  tpd2.level = 
                    TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (maintmpl));
                }

              /* Mark the template parameters.  But this time, we're
                 looking for the template parameters of the main
                 template, not in the specialization.  */
              tpd2.current_arg = i;
              tpd2.arg_uses_template_parms[i] = 0;
              bzero ((PTR) tpd2.parms, sizeof (int) * nargs);
              for_each_template_parm (type,
                                      &mark_template_parm,
                                      &tpd2);
                  
              if (tpd2.arg_uses_template_parms [i])
                {
                  /* The type depended on some template parameters.
                     If they are fully specialized in the
                     specialization, that's OK.  */
                  int j;
                  for (j = 0; j < nargs; ++j)
                    if (tpd2.parms[j] != 0
                        && tpd.arg_uses_template_parms [j])
                      {
                        cp_error ("type `%T' of template argument `%E' depends on template parameter(s)", 
                                  type,
                                  arg);
                        break;
                      }
                }
            }
        }
    }

  if (retrieve_specialization (maintmpl, specargs))
    /* We've already got this specialization.  */
    return decl;

  DECL_TEMPLATE_SPECIALIZATIONS (maintmpl) = CLASSTYPE_TI_SPEC_INFO (type)
    = perm_tree_cons (inner_args, inner_parms,
                      DECL_TEMPLATE_SPECIALIZATIONS (maintmpl));
  TREE_TYPE (DECL_TEMPLATE_SPECIALIZATIONS (maintmpl)) = type;
  return decl;
}

/* Check that a template declaration's use of default arguments is not
   invalid.  Here, PARMS are the template parameters.  IS_PRIMARY is
   non-zero if DECL is the thing declared by a primary template.
   IS_PARTIAL is non-zero if DECL is a partial specialization.  */

static void
check_default_tmpl_args (decl, parms, is_primary, is_partial)
     tree decl;
     tree parms;
     int is_primary;
     int is_partial;
{
  char* msg;
  int   last_level_to_check;

  /* [temp.param] 

     A default template-argument shall not be specified in a
     function template declaration or a function template definition, nor
     in the template-parameter-list of the definition of a member of a
     class template.  */

  if (current_class_type
      && !TYPE_BEING_DEFINED (current_class_type)
      && DECL_REAL_CONTEXT (decl) == current_class_type
      && DECL_DEFINED_IN_CLASS_P (decl)) 
    /* We already checked these parameters when the template was
       declared, so there's no need to do it again now.  This is an
       inline member function definition.  */
    return;

  if (TREE_CODE (decl) != TYPE_DECL || is_partial || !is_primary)
    /* For an ordinary class template, default template arguments are
       allowed at the innermost level, e.g.:
         template <class T = int>
         struct S {};
       but, in a partial specialization, they're not allowed even
       there, as we have in [temp.class.spec]:
     
         The template parameter list of a specialization shall not
         contain default template argument values.  

       So, for a partial specialization, or for a function template,
       we look at all of them.  */
    ;
  else
    /* But, for a primary class template that is not a partial
       specialization we look at all template parameters except the
       innermost ones.  */
    parms = TREE_CHAIN (parms);

  /* Figure out what error message to issue.  */
  if (TREE_CODE (decl) == FUNCTION_DECL)
    msg = "default argument for template parameter in function template `%D'";
  else if (is_partial)
    msg = "default argument in partial specialization `%D'";
  else
    msg = "default argument for template parameter for class enclosing `%D'";

  if (current_class_type && TYPE_BEING_DEFINED (current_class_type))
    /* If we're inside a class definition, there's no need to
       examine the parameters to the class itself.  On the one
       hand, they will be checked when the class is defined, and,
       on the other, default arguments are legal in things like:
         template <class T = double>
         struct S { template <class U> void f(U); };
       Here the default argument for `S' has no bearing on the
       declaration of `f'.  */
    last_level_to_check = template_class_depth (current_class_type) + 1;
  else
    /* Check everything.  */
    last_level_to_check = 0;

  for (; parms && TMPL_PARMS_DEPTH (parms) >= last_level_to_check; 
       parms = TREE_CHAIN (parms))
    {
      tree inner_parms = TREE_VALUE (parms);
      int i, ntparms;

      ntparms = TREE_VEC_LENGTH (inner_parms);
      for (i = 0; i < ntparms; ++i) 
        if (TREE_PURPOSE (TREE_VEC_ELT (inner_parms, i)))
          {
            if (msg)
              {
                cp_error (msg, decl);
                msg = 0;
              }

            /* Clear out the default argument so that we are not
               confused later.  */
            TREE_PURPOSE (TREE_VEC_ELT (inner_parms, i)) = NULL_TREE;
          }

      /* At this point, if we're still interested in issuing messages,
         they must apply to classes surrounding the object declared.  */
      if (msg)
        msg = "default argument for template parameter for class enclosing `%D'"; 
    }
}

/* Creates a TEMPLATE_DECL for the indicated DECL using the template
   parameters given by current_template_args, or reuses a
   previously existing one, if appropriate.  Returns the DECL, or an
   equivalent one, if it is replaced via a call to duplicate_decls.  

   If IS_FRIEND is non-zero, DECL is a friend declaration.  */

tree
push_template_decl_real (decl, is_friend)
     tree decl;
     int is_friend;
{
  tree tmpl;
  tree args;
  tree info;
  tree ctx;
  int primary;
  int is_partial;

  /* See if this is a partial specialization.  */
  is_partial = (TREE_CODE (decl) == TYPE_DECL && DECL_ARTIFICIAL (decl)
                && TREE_CODE (TREE_TYPE (decl)) != ENUMERAL_TYPE
                && CLASSTYPE_TEMPLATE_SPECIALIZATION (TREE_TYPE (decl)));

  is_friend |= (TREE_CODE (decl) == FUNCTION_DECL && DECL_FRIEND_P (decl));

  if (is_friend)
    /* For a friend, we want the context of the friend function, not
       the type of which it is a friend.  */
    ctx = DECL_CONTEXT (decl);
  else if (DECL_REAL_CONTEXT (decl)
           && TREE_CODE (DECL_REAL_CONTEXT (decl)) != NAMESPACE_DECL)
    /* In the case of a virtual function, we want the class in which
       it is defined.  */
    ctx = DECL_REAL_CONTEXT (decl);
  else
    /* Otherwise, if we're currently definining some class, the DECL
       is assumed to be a member of the class.  */
    ctx = current_class_type;

  if (ctx && TREE_CODE (ctx) == NAMESPACE_DECL)
    ctx = NULL_TREE;

  if (!DECL_CONTEXT (decl))
    DECL_CONTEXT (decl) = FROB_CONTEXT (current_namespace);

  /* For determining whether this is a primary template or not, we're really
     interested in the lexical context, not the true context.  */
  if (is_friend)
    info = current_class_type;
  else
    info = ctx;

  /* See if this is a primary template.  */
  if (info && TREE_CODE (info) == FUNCTION_DECL)
    primary = 0;
  /* Note that template_class_depth returns 0 if given NULL_TREE, so
     this next line works even when we are at global scope.  */
  else if (processing_template_decl > template_class_depth (info))
    primary = 1;
  else
    primary = 0;

  if (primary)
    {
      if (current_lang_name == lang_name_c)
        cp_error ("template with C linkage");
      if (TREE_CODE (decl) == TYPE_DECL && ANON_AGGRNAME_P (DECL_NAME (decl)))
        cp_error ("template class without a name");
      if (TREE_CODE (decl) == TYPE_DECL 
          && TREE_CODE (TREE_TYPE (decl)) == ENUMERAL_TYPE)
        cp_error ("template declaration of `%#T'", TREE_TYPE (decl));
    }

  /* Check to see that the rules regarding the use of default
     arguments are not being violated.  */
  check_default_tmpl_args (decl, current_template_parms, 
                           primary, is_partial);

  if (is_partial)
    return process_partial_specialization (decl);

  args = current_template_args ();

  if (!ctx 
      || TREE_CODE (ctx) == FUNCTION_DECL
      || TYPE_BEING_DEFINED (ctx)
      || (is_friend && !DECL_TEMPLATE_INFO (decl)))
    {
      if (DECL_LANG_SPECIFIC (decl)
          && DECL_TEMPLATE_INFO (decl)
          && DECL_TI_TEMPLATE (decl))
        tmpl = DECL_TI_TEMPLATE (decl);
      else
        {
          tmpl = build_template_decl (decl, current_template_parms);
          
          if (DECL_LANG_SPECIFIC (decl)
              && DECL_TEMPLATE_SPECIALIZATION (decl))
            {
              /* A specialization of a member template of a template
                 class. */
              SET_DECL_TEMPLATE_SPECIALIZATION (tmpl);
              DECL_TEMPLATE_INFO (tmpl) = DECL_TEMPLATE_INFO (decl);
              DECL_TEMPLATE_INFO (decl) = NULL_TREE;
            }
        }
    }
  else
    {
      tree a, t, current, parms;
      int i;

      if (CLASSTYPE_TEMPLATE_INSTANTIATION (ctx))
        cp_error ("must specialize `%#T' before defining member `%#D'",
                  ctx, decl);
      if (TREE_CODE (decl) == TYPE_DECL)
        {
          if ((IS_AGGR_TYPE_CODE (TREE_CODE (TREE_TYPE (decl)))
               || TREE_CODE (TREE_TYPE (decl)) == ENUMERAL_TYPE)
              && TYPE_TEMPLATE_INFO (TREE_TYPE (decl))
              && TYPE_TI_TEMPLATE (TREE_TYPE (decl)))
            tmpl = TYPE_TI_TEMPLATE (TREE_TYPE (decl));
          else
            {
              cp_error ("`%D' does not declare a template type", decl);
              return decl;
            }
        }
      else if (! DECL_TEMPLATE_INFO (decl))
        {
          cp_error ("template definition of non-template `%#D'", decl);
          return decl;
        }
      else
        tmpl = DECL_TI_TEMPLATE (decl);
      
      if (is_member_template (tmpl)
          && DECL_FUNCTION_TEMPLATE_P (tmpl)
          && DECL_TEMPLATE_INFO (decl) && DECL_TI_ARGS (decl) 
          && DECL_TEMPLATE_SPECIALIZATION (decl))
        {
          tree new_tmpl;

          /* The declaration is a specialization of a member
             template, declared outside the class.  Therefore, the
             innermost template arguments will be NULL, so we
             replace them with the arguments determined by the
             earlier call to check_explicit_specialization.  */
          args = DECL_TI_ARGS (decl);

          new_tmpl 
            = build_template_decl (decl, current_template_parms);
          DECL_TEMPLATE_RESULT (new_tmpl) = decl;
          TREE_TYPE (new_tmpl) = TREE_TYPE (decl);
          DECL_TI_TEMPLATE (decl) = new_tmpl;
          SET_DECL_TEMPLATE_SPECIALIZATION (new_tmpl);
          DECL_TEMPLATE_INFO (new_tmpl) = 
            perm_tree_cons (tmpl, args, NULL_TREE);

          register_specialization (new_tmpl, tmpl, args);
          return decl;
        }

      /* Make sure the template headers we got make sense.  */

      parms = DECL_TEMPLATE_PARMS (tmpl);
      i = TMPL_PARMS_DEPTH (parms);
      if (TMPL_ARGS_DEPTH (args) != i)
        {
          cp_error ("expected %d levels of template parms for `%#D', got %d",
                    i, decl, TMPL_ARGS_DEPTH (args));
        }
      else
        for (current = decl; i > 0; --i, parms = TREE_CHAIN (parms))
          {
            a = TMPL_ARGS_LEVEL (args, i);
            t = INNERMOST_TEMPLATE_PARMS (parms);

            if (TREE_VEC_LENGTH (t) != TREE_VEC_LENGTH (a))
              {
                if (current == decl)
                  cp_error ("got %d template parameters for `%#D'",
                            TREE_VEC_LENGTH (a), decl);
                else
                  cp_error ("got %d template parameters for `%#T'",
                            TREE_VEC_LENGTH (a), current);
                cp_error ("  but %d required", TREE_VEC_LENGTH (t));
              }

            /* Perhaps we should also check that the parms are used in the
               appropriate qualifying scopes in the declarator?  */

            if (current == decl)
              current = ctx;
            else
              current = TYPE_CONTEXT (current);
          }
    }

  DECL_TEMPLATE_RESULT (tmpl) = decl;
  TREE_TYPE (tmpl) = TREE_TYPE (decl);

  /* Push template declarations for global functions and types.  Note
     that we do not try to push a global template friend declared in a
     template class; such a thing may well depend on the template
     parameters of the class.  */
  if (! ctx 
      && !(is_friend && template_class_depth (current_class_type) > 0))
    tmpl = pushdecl_namespace_level (tmpl);

  if (primary)
    DECL_PRIMARY_TEMPLATE (tmpl) = tmpl;

  info = perm_tree_cons (tmpl, args, NULL_TREE);

  if (TREE_CODE (decl) == TYPE_DECL && DECL_ARTIFICIAL (decl))
    {
      SET_TYPE_TEMPLATE_INFO (TREE_TYPE (tmpl), info);
      if ((!ctx || TREE_CODE (ctx) != FUNCTION_DECL)
          && TREE_CODE (TREE_TYPE (decl)) != ENUMERAL_TYPE)
        DECL_NAME (decl) = classtype_mangled_name (TREE_TYPE (decl));
    }
  else if (! DECL_LANG_SPECIFIC (decl))
    cp_error ("template declaration of `%#D'", decl);
  else
    DECL_TEMPLATE_INFO (decl) = info;

  return DECL_TEMPLATE_RESULT (tmpl);
}

tree
push_template_decl (decl)
     tree decl;
{
  return push_template_decl_real (decl, 0);
}

/* Called when a class template TYPE is redeclared with the indicated
   template PARMS, e.g.:

     template <class T> struct S;
     template <class T> struct S {};  */

void 
redeclare_class_template (type, parms)
     tree type;
     tree parms;
{
  tree tmpl = CLASSTYPE_TI_TEMPLATE (type);
  tree tmpl_parms;
  int i;

  if (!PRIMARY_TEMPLATE_P (tmpl))
    /* The type is nested in some template class.  Nothing to worry
       about here; there are no new template parameters for the nested
       type.  */
    return;

  parms = INNERMOST_TEMPLATE_PARMS (parms);
  tmpl_parms = DECL_INNERMOST_TEMPLATE_PARMS (tmpl);

  if (TREE_VEC_LENGTH (parms) != TREE_VEC_LENGTH (tmpl_parms))
    {
      cp_error_at ("previous declaration `%D'", tmpl);
      cp_error ("used %d template parameter%s instead of %d",
                TREE_VEC_LENGTH (tmpl_parms), 
                TREE_VEC_LENGTH (tmpl_parms) == 1 ? "" : "s",
                TREE_VEC_LENGTH (parms));
      return;
    }

  for (i = 0; i < TREE_VEC_LENGTH (tmpl_parms); ++i)
    {
      tree tmpl_parm = TREE_VALUE (TREE_VEC_ELT (tmpl_parms, i));
      tree parm = TREE_VALUE (TREE_VEC_ELT (parms, i));
      tree tmpl_default = TREE_PURPOSE (TREE_VEC_ELT (tmpl_parms, i));
      tree parm_default = TREE_PURPOSE (TREE_VEC_ELT (parms, i));

      if (TREE_CODE (tmpl_parm) != TREE_CODE (parm))
        {
          cp_error_at ("template parameter `%#D'", tmpl_parm);
          cp_error ("redeclared here as `%#D'", parm);
          return;
        }

      if (tmpl_default != NULL_TREE && parm_default != NULL_TREE)
        {
          /* We have in [temp.param]:

             A template-parameter may not be given default arguments
             by two different declarations in the same scope.  */
          cp_error ("redefinition of default argument for `%#D'", parm);
          cp_error_at ("  original definition appeared here", tmpl_parm);
          return;
        }

      if (parm_default != NULL_TREE)
        /* Update the previous template parameters (which are the ones
           that will really count) with the new default value.  */
        TREE_PURPOSE (TREE_VEC_ELT (tmpl_parms, i)) = parm_default;
    }
}

/* Attempt to convert the non-type template parameter EXPR to the
   indicated TYPE.  If the conversion is successful, return the
   converted value.  If the conversion is unsuccesful, return
   NULL_TREE if we issued an error message, or error_mark_node if we
   did not.  We issue error messages for out-and-out bad template
   parameters, but not simply because the conversion failed, since we
   might be just trying to do argument deduction.  By the time this
   function is called, neither TYPE nor EXPR may make use of template
   parameters.  */

static tree
convert_nontype_argument (type, expr)
     tree type;
     tree expr;
{
  tree expr_type = TREE_TYPE (expr);

  /* A template-argument for a non-type, non-template
     template-parameter shall be one of:

     --an integral constant-expression of integral or enumeration
     type; or
     
     --the name of a non-type template-parameter; or
     
     --the name of an object or function with external linkage,
     including function templates and function template-ids but
     excluding non-static class members, expressed as id-expression;
     or
     
     --the address of an object or function with external linkage,
     including function templates and function template-ids but
     excluding non-static class members, expressed as & id-expression
     where the & is optional if the name refers to a function or
     array; or
     
     --a pointer to member expressed as described in _expr.unary.op_.  */

  /* An integral constant-expression can include const variables
     or enumerators.  */
  if (INTEGRAL_TYPE_P (expr_type) && TREE_READONLY_DECL_P (expr))
    expr = decl_constant_value (expr);

  if (is_overloaded_fn (expr))
    /* OK for now.  We'll check that it has external linkage later.
       Check this first since if expr_type is the unknown_type_node
       we would otherwise complain below.  */
    ;
  else if (TYPE_PTR_P (expr_type)
           || TREE_CODE (expr_type) == ARRAY_TYPE
           || TREE_CODE (type) == REFERENCE_TYPE
           /* If expr is the address of an overloaded function, we
              will get the unknown_type_node at this point.  */
           || expr_type == unknown_type_node)
    {
      tree referent;
      tree e = expr;
      STRIP_NOPS (e);

      if (TREE_CODE (type) == REFERENCE_TYPE
          || TREE_CODE (expr_type) == ARRAY_TYPE)
        referent = e;
      else
        {
          if (TREE_CODE (e) != ADDR_EXPR)
            {
            bad_argument:
              cp_error ("`%E' is not a valid template argument", expr);
              error ("it must be %s%s with external linkage",
                     TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE
                     ? "a pointer to " : "",
                     TREE_CODE (TREE_TYPE (TREE_TYPE (expr))) == FUNCTION_TYPE
                     ? "a function" : "an object");
              return NULL_TREE;
            }

          referent = TREE_OPERAND (e, 0);
          STRIP_NOPS (referent);
        }

      if (TREE_CODE (referent) == STRING_CST)
        {
          cp_error ("string literal %E is not a valid template argument", 
                    referent);
          error ("because it is the address of an object with static linkage");
          return NULL_TREE;
        }

      if (is_overloaded_fn (referent))
        /* We'll check that it has external linkage later.  */
        ;
      else if (TREE_CODE (referent) != VAR_DECL)
        goto bad_argument;
      else if (!TREE_PUBLIC (referent))
        {
          cp_error ("address of non-extern `%E' cannot be used as template argument", referent); 
          return error_mark_node;
        }
    }
  else if (INTEGRAL_TYPE_P (expr_type) 
           || TYPE_PTRMEM_P (expr_type) 
           || TYPE_PTRMEMFUNC_P (expr_type)
           /* The next two are g++ extensions.  */
           || TREE_CODE (expr_type) == REAL_TYPE
           || TREE_CODE (expr_type) == COMPLEX_TYPE)
    {
      if (! TREE_CONSTANT (expr))
        {
        non_constant:
          cp_error ("non-constant `%E' cannot be used as template argument",
                    expr);
          return NULL_TREE;
        }
    }
  else 
    {
      cp_error ("object `%E' cannot be used as template argument", expr);
      return NULL_TREE;
    }

  switch (TREE_CODE (type))
    {
    case INTEGER_TYPE:
    case BOOLEAN_TYPE:
    case ENUMERAL_TYPE:
      /* For a non-type template-parameter of integral or enumeration
         type, integral promotions (_conv.prom_) and integral
         conversions (_conv.integral_) are applied. */
      if (!INTEGRAL_TYPE_P (expr_type))
        return error_mark_node;
      
      /* It's safe to call digest_init in this case; we know we're
         just converting one integral constant expression to another.  */
      expr = digest_init (type, expr, (tree*) 0);

      if (TREE_CODE (expr) != INTEGER_CST)
        /* Curiously, some TREE_CONSTANT integral expressions do not
           simplify to integer constants.  For example, `3 % 0',
           remains a TRUNC_MOD_EXPR.  */
        goto non_constant;
      
      return expr;
        
    case REAL_TYPE:
    case COMPLEX_TYPE:
      /* These are g++ extensions.  */
      if (TREE_CODE (expr_type) != TREE_CODE (type))
        return error_mark_node;

      expr = digest_init (type, expr, (tree*) 0);
      
      if (TREE_CODE (expr) != REAL_CST)
        goto non_constant;

      return expr;

    case POINTER_TYPE:
      {
        tree type_pointed_to = TREE_TYPE (type);
 
        if (TYPE_PTRMEM_P (type))
          /* For a non-type template-parameter of type pointer to data
             member, qualification conversions (_conv.qual_) are
             applied.  */
          return perform_qualification_conversions (type, expr);
        else if (TREE_CODE (type_pointed_to) == FUNCTION_TYPE)
          { 
            /* For a non-type template-parameter of type pointer to
               function, only the function-to-pointer conversion
               (_conv.func_) is applied.  If the template-argument
               represents a set of overloaded functions (or a pointer to
               such), the matching function is selected from the set
               (_over.over_).  */
            tree fns;
            tree fn;

            if (TREE_CODE (expr) == ADDR_EXPR)
              fns = TREE_OPERAND (expr, 0);
            else
              fns = expr;

            fn = instantiate_type (type_pointed_to, fns, 0);

            if (fn == error_mark_node)
              return error_mark_node;

            if (!TREE_PUBLIC (fn))
              {
                if (really_overloaded_fn (fns))
                  return error_mark_node;
                else
                  goto bad_argument;
              }

            expr = build_unary_op (ADDR_EXPR, fn, 0);

            my_friendly_assert (same_type_p (type, TREE_TYPE (expr)), 
                                0);
            return expr;
          }
        else 
          {
            /* For a non-type template-parameter of type pointer to
               object, qualification conversions (_conv.qual_) and the
               array-to-pointer conversion (_conv.array_) are applied.
               [Note: In particular, neither the null pointer conversion
               (_conv.ptr_) nor the derived-to-base conversion
               (_conv.ptr_) are applied.  Although 0 is a valid
               template-argument for a non-type template-parameter of
               integral type, it is not a valid template-argument for a
               non-type template-parameter of pointer type.]  
            
               The call to decay_conversion performs the
               array-to-pointer conversion, if appropriate.  */
            expr = decay_conversion (expr);

            if (expr == error_mark_node)
              return error_mark_node;
            else
              return perform_qualification_conversions (type, expr);
          }
      }
      break;

    case REFERENCE_TYPE:
      {
        tree type_referred_to = TREE_TYPE (type);

        if (TREE_CODE (type_referred_to) == FUNCTION_TYPE)
          {
            /* For a non-type template-parameter of type reference to
               function, no conversions apply.  If the
               template-argument represents a set of overloaded
               functions, the matching function is selected from the
               set (_over.over_).  */
            tree fns = expr;
            tree fn;

            fn = instantiate_type (type_referred_to, fns, 0);

            if (fn == error_mark_node)
              return error_mark_node;

            if (!TREE_PUBLIC (fn))
              {
                if (really_overloaded_fn (fns))
                  /* Don't issue an error here; we might get a different
                     function if the overloading had worked out
                     differently.  */
                  return error_mark_node;
                else
                  goto bad_argument;
              }

            my_friendly_assert (same_type_p (type_referred_to, 
                                             TREE_TYPE (fn)),
                                0);

            return fn;
          }
        else
          {
            /* For a non-type template-parameter of type reference to
               object, no conversions apply.  The type referred to by the
               reference may be more cv-qualified than the (otherwise
               identical) type of the template-argument.  The
               template-parameter is bound directly to the
               template-argument, which must be an lvalue.  */
            if ((TYPE_MAIN_VARIANT (expr_type)
                 != TYPE_MAIN_VARIANT (type_referred_to))
                || !at_least_as_qualified_p (type_referred_to,
                                             expr_type)
                || !real_lvalue_p (expr))
              return error_mark_node;
            else
              return expr;
          }
      }
      break;

    case RECORD_TYPE:
      {
        if (!TYPE_PTRMEMFUNC_P (type))
          /* This handles templates like
               template<class T, T t> void f();
             when T is substituted with any class.  The second template
             parameter becomes invalid and the template candidate is
             rejected.  */
          return error_mark_node;

        /* For a non-type template-parameter of type pointer to member
           function, no conversions apply.  If the template-argument
           represents a set of overloaded member functions, the
           matching member function is selected from the set
           (_over.over_).  */

        if (!TYPE_PTRMEMFUNC_P (expr_type) && 
            expr_type != unknown_type_node)
          return error_mark_node;

        if (TREE_CODE (expr) == CONSTRUCTOR)
          {
            /* A ptr-to-member constant.  */
            if (!same_type_p (type, expr_type))
              return error_mark_node;
            else 
              return expr;
          }

        if (TREE_CODE (expr) != ADDR_EXPR)
          return error_mark_node;

        expr = instantiate_type (type, expr, 0);
        
        if (expr == error_mark_node)
          return error_mark_node;

        my_friendly_assert (same_type_p (type, TREE_TYPE (expr)),
                            0);
        return expr;
      }
      break;

    default:
      /* All non-type parameters must have one of these types.  */
      my_friendly_abort (0);
      break;
    }

  return error_mark_node;
}

/* Return 1 if PARM_PARMS and ARG_PARMS matches using rule for 
   template template parameters.  Both PARM_PARMS and ARG_PARMS are 
   vectors of TREE_LIST nodes containing TYPE_DECL, TEMPLATE_DECL 
   or PARM_DECL.
   
   ARG_PARMS may contain more parameters than PARM_PARMS.  If this is 
   the case, then extra parameters must have default arguments.

   Consider the example:
     template <class T, class Allocator = allocator> class vector;
     template<template <class U> class TT> class C;

   C<vector> is a valid instantiation.  PARM_PARMS for the above code 
   contains a TYPE_DECL (for U),  ARG_PARMS contains two TYPE_DECLs (for 
   T and Allocator) and OUTER_ARGS contains the argument that is used to 
   substitute the TT parameter.  */

static int
coerce_template_template_parms (parm_parms, arg_parms, complain, 
                                in_decl, outer_args)
     tree parm_parms, arg_parms;
     int complain;
     tree in_decl, outer_args;
{
  int nparms, nargs, i;
  tree parm, arg;

  my_friendly_assert (TREE_CODE (parm_parms) == TREE_VEC, 0);
  my_friendly_assert (TREE_CODE (arg_parms) == TREE_VEC, 0);

  nparms = TREE_VEC_LENGTH (parm_parms);
  nargs = TREE_VEC_LENGTH (arg_parms);

  /* The rule here is opposite of coerce_template_parms.  */
  if (nargs < nparms
      || (nargs > nparms
          && TREE_PURPOSE (TREE_VEC_ELT (arg_parms, nparms)) == NULL_TREE))
    return 0;

  for (i = 0; i < nparms; ++i)
    {
      parm = TREE_VALUE (TREE_VEC_ELT (parm_parms, i));
      arg = TREE_VALUE (TREE_VEC_ELT (arg_parms, i));

      if (arg == NULL_TREE || arg == error_mark_node
          || parm == NULL_TREE || parm == error_mark_node)
        return 0;

      if (TREE_CODE (arg) != TREE_CODE (parm))
        return 0;

      switch (TREE_CODE (parm))
        {
        case TYPE_DECL:
          break;

        case TEMPLATE_DECL:
          /* We encounter instantiations of templates like
               template <template <template <class> class> class TT>
               class C;  */
          {
            tree parmparm = DECL_INNERMOST_TEMPLATE_PARMS (parm);
            tree argparm = DECL_INNERMOST_TEMPLATE_PARMS (arg);

            if (!coerce_template_template_parms (parmparm, argparm, 
                                                 complain, in_decl,
                                                 outer_args))
              return 0;
          }
          break;

        case PARM_DECL:
          /* The tsubst call is used to handle cases such as
               template <class T, template <T> class TT> class D;  
             i.e. the parameter list of TT depends on earlier parameters.  */
          if (!same_type_p (tsubst (TREE_TYPE (parm), outer_args, 
                                    complain, in_decl),
                            TREE_TYPE (arg)))
            return 0;
          break;
          
        default:
          my_friendly_abort (0);
        }
    }
  return 1;
}

/* Convert the indicated template ARG as necessary to match the
   indicated template PARM.  Returns the converted ARG, or
   error_mark_node if the conversion was unsuccessful.  Error messages
   are issued if COMPLAIN is non-zero.  This conversion is for the Ith
   parameter in the parameter list.  ARGS is the full set of template
   arguments deduced so far.  */

static tree
convert_template_argument (parm, arg, args, complain, i, in_decl)
     tree parm;
     tree arg;
     tree args;
     int complain;
     int i;
     tree in_decl;
{
  tree val;
  tree inner_args;
  int is_type, requires_type, is_tmpl_type, requires_tmpl_type;
  
  inner_args = innermost_args (args);

  if (TREE_CODE (arg) == TREE_LIST 
      && TREE_TYPE (arg) != NULL_TREE
      && TREE_CODE (TREE_TYPE (arg)) == OFFSET_TYPE)
    {  
      /* The template argument was the name of some
         member function.  That's usually
         illegal, but static members are OK.  In any
         case, grab the underlying fields/functions
         and issue an error later if required.  */
      arg = TREE_VALUE (arg);
      TREE_TYPE (arg) = unknown_type_node;
    }

  requires_tmpl_type = TREE_CODE (parm) == TEMPLATE_DECL;
  requires_type = (TREE_CODE (parm) == TYPE_DECL
                   || requires_tmpl_type);

  /* Check if it is a class template.  If REQUIRES_TMPL_TYPE is true,
     we also accept implicitly created TYPE_DECL as a valid argument.
     This is necessary to handle the case where we pass a template name
     to a template template parameter in a scope where we've derived from
     in instantiation of that template, so the template name refers to that
     instantiation.  We really ought to handle this better.  */
  is_tmpl_type 
    = ((TREE_CODE (arg) == TEMPLATE_DECL
        && TREE_CODE (DECL_TEMPLATE_RESULT (arg)) == TYPE_DECL)
       || (TREE_CODE (arg) == TEMPLATE_TEMPLATE_PARM
           && !TEMPLATE_TEMPLATE_PARM_TEMPLATE_INFO (arg))
       || (TREE_CODE (arg) == RECORD_TYPE
           && CLASSTYPE_TEMPLATE_INFO (arg)
           && TREE_CODE (TYPE_NAME (arg)) == TYPE_DECL
           && DECL_ARTIFICIAL (TYPE_NAME (arg))
           && requires_tmpl_type
           && is_base_of_enclosing_class (arg, current_class_type)));
  if (is_tmpl_type && TREE_CODE (arg) == TEMPLATE_TEMPLATE_PARM)
    arg = TYPE_STUB_DECL (arg);
  else if (is_tmpl_type && TREE_CODE (arg) == RECORD_TYPE)
    arg = CLASSTYPE_TI_TEMPLATE (arg);

  is_type = TREE_CODE_CLASS (TREE_CODE (arg)) == 't' || is_tmpl_type;

  if (requires_type && ! is_type && TREE_CODE (arg) == SCOPE_REF
      && TREE_CODE (TREE_OPERAND (arg, 0)) == TEMPLATE_TYPE_PARM)
    {
      cp_pedwarn ("to refer to a type member of a template parameter,");
      cp_pedwarn ("  use `typename %E'", arg);
      
      arg = make_typename_type (TREE_OPERAND (arg, 0),
                                TREE_OPERAND (arg, 1));
      is_type = 1;
    }
  if (is_type != requires_type)
    {
      if (in_decl)
        {
          if (complain)
            {
              cp_error ("type/value mismatch at argument %d in template parameter list for `%D'",
                        i + 1, in_decl);
              if (is_type)
                cp_error ("  expected a constant of type `%T', got `%T'",
                          TREE_TYPE (parm),
                          (is_tmpl_type ? DECL_NAME (arg) : arg));
              else
                cp_error ("  expected a type, got `%E'", arg);
            }
        }
      return error_mark_node;
    }
  if (is_tmpl_type ^ requires_tmpl_type)
    {
      if (in_decl && complain)
        {
          cp_error ("type/value mismatch at argument %d in template parameter list for `%D'",
                    i + 1, in_decl);
          if (is_tmpl_type)
            cp_error ("  expected a type, got `%T'", DECL_NAME (arg));
          else
            cp_error ("  expected a class template, got `%T'", arg);
        }
      return error_mark_node;
    }
      
  if (is_type)
    {
      if (requires_tmpl_type)
        {
          tree parmparm = DECL_INNERMOST_TEMPLATE_PARMS (parm);
          tree argparm = DECL_INNERMOST_TEMPLATE_PARMS (arg);

          if (coerce_template_template_parms (parmparm, argparm, complain,
                                              in_decl, inner_args))
            {
              val = arg;
                  
              /* TEMPLATE_TEMPLATE_PARM node is preferred over 
                 TEMPLATE_DECL.  */
              if (val != error_mark_node 
                  && DECL_TEMPLATE_TEMPLATE_PARM_P (val))
                val = TREE_TYPE (val);
            }
          else
            {
              if (in_decl && complain)
                {
                  cp_error ("type/value mismatch at argument %d in template parameter list for `%D'",
                            i + 1, in_decl);
                  cp_error ("  expected a template of type `%D', got `%D'", parm, arg);
                }
                  
              val = error_mark_node;
            }
        }
      else
        {
          val = groktypename (arg);
          if (! processing_template_decl)
            {
              /* [basic.link]: A name with no linkage (notably, the
                 name of a class or enumeration declared in a local
                 scope) shall not be used to declare an entity with
                 linkage.  This implies that names with no linkage
                 cannot be used as template arguments.  */
              tree t = no_linkage_check (val);
              if (t)
                {
                  if (ANON_AGGRNAME_P (TYPE_IDENTIFIER (t)))
                    cp_pedwarn
                      ("template-argument `%T' uses anonymous type", val);
                  else
                    cp_error
                      ("template-argument `%T' uses local type `%T'",
                       val, t);
                  return error_mark_node;
                }
            }
        }
    }
  else
    {
      tree t = tsubst (TREE_TYPE (parm), args, complain, in_decl);

      if (processing_template_decl)
        arg = maybe_fold_nontype_arg (arg);

      if (!uses_template_parms (arg) && !uses_template_parms (t))
        /* We used to call digest_init here.  However, digest_init
           will report errors, which we don't want when complain
           is zero.  More importantly, digest_init will try too
           hard to convert things: for example, `0' should not be
           converted to pointer type at this point according to
           the standard.  Accepting this is not merely an
           extension, since deciding whether or not these
           conversions can occur is part of determining which
           function template to call, or whether a given epxlicit
           argument specification is legal.  */
        val = convert_nontype_argument (t, arg);
      else
        val = arg;

      if (val == NULL_TREE)
        val = error_mark_node;
      else if (val == error_mark_node && complain)
        cp_error ("could not convert template argument `%E' to `%T'", 
                  arg, t);
    }

  return val;
}

/* Convert all template arguments to their appropriate types, and
   return a vector containing the innermost resulting template
   arguments.  If any error occurs, return error_mark_node, and, if
   COMPLAIN is non-zero, issue an error message.  Some error messages
   are issued even if COMPLAIN is zero; for instance, if a template
   argument is composed from a local class.

   If REQUIRE_ALL_ARGUMENTS is non-zero, all arguments must be
   provided in ARGLIST, or else trailing parameters must have default
   values.  If REQUIRE_ALL_ARGUMENTS is zero, we will attempt argument
   deduction for any unspecified trailing arguments.  

   The resulting TREE_VEC is allocated on a temporary obstack, and
   must be explicitly copied if it will be permanent.  */
   
static tree
coerce_template_parms (parms, args, in_decl,
                       complain,
                       require_all_arguments)
     tree parms, args;
     tree in_decl;
     int complain;
     int require_all_arguments;
{
  int nparms, nargs, i, lost = 0;
  tree inner_args;
  tree new_args;
  tree new_inner_args;

  inner_args = innermost_args (args);
  nargs = NUM_TMPL_ARGS (inner_args);
  nparms = TREE_VEC_LENGTH (parms);

  if (nargs > nparms
      || (nargs < nparms
          && require_all_arguments
          && TREE_PURPOSE (TREE_VEC_ELT (parms, nargs)) == NULL_TREE))
    {
      if (complain) 
        {
          cp_error ("wrong number of template arguments (%d, should be %d)",
                    nargs, nparms);
          
          if (in_decl)
            cp_error_at ("provided for `%D'", in_decl);
        }

      return error_mark_node;
    }

  new_inner_args = make_temp_vec (nparms);
  new_args = add_outermost_template_args (args, new_inner_args);
  for (i = 0; i < nparms; i++)
    {
      tree arg;
      tree parm;

      /* Get the Ith template parameter.  */
      parm = TREE_VEC_ELT (parms, i);

      /* Calculate the Ith argument.  */
      if (inner_args && TREE_CODE (inner_args) == TREE_LIST)
        {
          arg = TREE_VALUE (inner_args);
          inner_args = TREE_CHAIN (inner_args);
        }
      else if (i < nargs)
        arg = TREE_VEC_ELT (inner_args, i);
      /* If no template argument was supplied, look for a default
         value.  */
      else if (TREE_PURPOSE (parm) == NULL_TREE)
        {
          /* There was no default value.  */
          my_friendly_assert (!require_all_arguments, 0);
          break;
        }
      else if (TREE_CODE (TREE_VALUE (parm)) == TYPE_DECL)
        arg = tsubst (TREE_PURPOSE (parm), new_args, complain, in_decl);
      else
        arg = tsubst_expr (TREE_PURPOSE (parm), new_args, complain,
                           in_decl);

      /* Now, convert the Ith argument, as necessary.  */
      if (arg == NULL_TREE)
        /* We're out of arguments.  */
        {
          my_friendly_assert (!require_all_arguments, 0);
          break;
        }
      else if (arg == error_mark_node)
        {
          cp_error ("template argument %d is invalid", i + 1);
          arg = error_mark_node;
        }
      else 
        arg = convert_template_argument (TREE_VALUE (parm), 
                                         arg, new_args, complain, i,
                                         in_decl); 
      
      if (arg == error_mark_node)
        lost++;
      TREE_VEC_ELT (new_inner_args, i) = arg;
    }

  if (lost)
    return error_mark_node;

  return new_inner_args;
}

/* Returns 1 if template args OT and NT are equivalent.  */

int
template_args_equal (ot, nt)
     tree ot, nt;
{
  if (nt == ot)
    return 1;
  if (TREE_CODE (nt) != TREE_CODE (ot))
    return 0;
  if (TREE_CODE (nt) == TREE_VEC)
    /* For member templates */
    return comp_template_args (ot, nt);
  else if (TREE_CODE_CLASS (TREE_CODE (ot)) == 't')
    return same_type_p (ot, nt);
  else
    return (cp_tree_equal (ot, nt) > 0);
}

/* Returns 1 iff the OLDARGS and NEWARGS are in fact identical sets
   of template arguments.  Returns 0 otherwise.  */

int
comp_template_args (oldargs, newargs)
     tree oldargs, newargs;
{
  int i;

  if (TREE_VEC_LENGTH (oldargs) != TREE_VEC_LENGTH (newargs))
    return 0;

  for (i = 0; i < TREE_VEC_LENGTH (oldargs); ++i)
    {
      tree nt = TREE_VEC_ELT (newargs, i);
      tree ot = TREE_VEC_ELT (oldargs, i);

      if (! template_args_equal (ot, nt))
        return 0;
    }
  return 1;
}

/* Given class template name and parameter list, produce a user-friendly name
   for the instantiation.  */

static char *
mangle_class_name_for_template (name, parms, arglist)
     char *name;
     tree parms, arglist;
{
  static struct obstack scratch_obstack;
  static char *scratch_firstobj;
  int i, nparms;

  if (!scratch_firstobj)
    gcc_obstack_init (&scratch_obstack);
  else
    obstack_free (&scratch_obstack, scratch_firstobj);
  scratch_firstobj = obstack_alloc (&scratch_obstack, 1);

#define ccat(c) obstack_1grow (&scratch_obstack, (c));
#define cat(s)  obstack_grow (&scratch_obstack, (s), strlen (s))

  cat (name);
  ccat ('<');
  nparms = TREE_VEC_LENGTH (parms);
  arglist = innermost_args (arglist);
  my_friendly_assert (nparms == TREE_VEC_LENGTH (arglist), 268);
  for (i = 0; i < nparms; i++)
    {
      tree parm = TREE_VALUE (TREE_VEC_ELT (parms, i));
      tree arg = TREE_VEC_ELT (arglist, i);

      if (i)
        ccat (',');

      if (TREE_CODE (parm) == TYPE_DECL)
        {
          cat (type_as_string_real (arg, 0, 1));
          continue;
        }
      else if (TREE_CODE (parm) == TEMPLATE_DECL)
        {
          if (TREE_CODE (arg) == TEMPLATE_DECL)
            {
              /* Already substituted with real template.  Just output 
                 the template name here */
              tree context = DECL_CONTEXT (arg);
              if (context)
                {
                  my_friendly_assert (TREE_CODE (context) == NAMESPACE_DECL, 980422);
                  cat(decl_as_string (DECL_CONTEXT (arg), 0));
                  cat("::");
                }
              cat (IDENTIFIER_POINTER (DECL_NAME (arg)));
            }
          else
            /* Output the parameter declaration */
            cat (type_as_string_real (arg, 0, 1));
          continue;
        }
      else
        my_friendly_assert (TREE_CODE (parm) == PARM_DECL, 269);

      if (TREE_CODE (arg) == TREE_LIST)
        {
          /* New list cell was built because old chain link was in
             use.  */
          my_friendly_assert (TREE_PURPOSE (arg) == NULL_TREE, 270);
          arg = TREE_VALUE (arg);
        }
      /* No need to check arglist against parmlist here; we did that
         in coerce_template_parms, called from lookup_template_class.  */
      cat (expr_as_string (arg, 0));
    }
  {
    char *bufp = obstack_next_free (&scratch_obstack);
    int offset = 0;
    while (bufp[offset - 1] == ' ')
      offset--;
    obstack_blank_fast (&scratch_obstack, offset);

    /* B<C<char> >, not B<C<char>> */
    if (bufp[offset - 1] == '>')
      ccat (' ');
  }
  ccat ('>');
  ccat ('\0');
  return (char *) obstack_base (&scratch_obstack);
}

static tree
classtype_mangled_name (t)
     tree t;
{
  if (CLASSTYPE_TEMPLATE_INFO (t)
      /* Specializations have already had their names set up in
         lookup_template_class.  */
      && !CLASSTYPE_TEMPLATE_SPECIALIZATION (t))
    {
      tree tmpl = most_general_template (CLASSTYPE_TI_TEMPLATE (t));

      /* For non-primary templates, the template parameters are
         implicit from their surrounding context.  */
      if (PRIMARY_TEMPLATE_P (tmpl))
        {
          tree name = DECL_NAME (tmpl);
          char *mangled_name = mangle_class_name_for_template
            (IDENTIFIER_POINTER (name), 
             DECL_INNERMOST_TEMPLATE_PARMS (tmpl),
             CLASSTYPE_TI_ARGS (t));
          tree id = get_identifier (mangled_name);
          IDENTIFIER_TEMPLATE (id) = name;
          return id;
        }
    }

  return TYPE_IDENTIFIER (t);
}

static void
add_pending_template (d)
     tree d;
{
  tree ti;

  if (TREE_CODE_CLASS (TREE_CODE (d)) == 't')
    ti = CLASSTYPE_TEMPLATE_INFO (d);
  else
    ti = DECL_TEMPLATE_INFO (d);

  if (TI_PENDING_TEMPLATE_FLAG (ti))
    return;

  *template_tail = perm_tree_cons
    (build_srcloc_here (), d, NULL_TREE);
  template_tail = &TREE_CHAIN (*template_tail);
  TI_PENDING_TEMPLATE_FLAG (ti) = 1;
}


/* Return a TEMPLATE_ID_EXPR corresponding to the indicated FNS (which
   may be either a _DECL or an overloaded function or an
   IDENTIFIER_NODE), and ARGLIST.  */

tree
lookup_template_function (fns, arglist)
     tree fns, arglist;
{
  tree type;

  if (fns == NULL_TREE)
    {
      cp_error ("non-template used as template");
      return error_mark_node;
    }

  type = TREE_TYPE (fns);
  if (TREE_CODE (fns) == OVERLOAD || !type)
    type = unknown_type_node;

  if (processing_template_decl)
    return build_min (TEMPLATE_ID_EXPR, type, fns, arglist);  
  else
    return build (TEMPLATE_ID_EXPR, type, fns, arglist);
}

/* Within the scope of a template class S<T>, the name S gets bound
   (in build_self_reference) to a TYPE_DECL for the class, not a
   TEMPLATE_DECL.  If DECL is a TYPE_DECL for current_class_type,
   or one of its enclosing classes, and that type is a template,
   return the associated TEMPLATE_DECL.  Otherwise, the original
   DECL is returned.  */

static tree
maybe_get_template_decl_from_type_decl (decl)
     tree decl;
{
  return (decl != NULL_TREE
          && TREE_CODE (decl) == TYPE_DECL 
          && DECL_ARTIFICIAL (decl)
          && CLASSTYPE_TEMPLATE_INFO (TREE_TYPE (decl))) 
    ? CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl)) : decl;
}

/* Given an IDENTIFIER_NODE (type TEMPLATE_DECL) and a chain of
   parameters, find the desired type.

   D1 is the PTYPENAME terminal, and ARGLIST is the list of arguments.
   (Actually ARGLIST may be either a TREE_LIST or a TREE_VEC.  It will
   be a TREE_LIST if called directly from the parser, and a TREE_VEC
   otherwise.)  Since ARGLIST is build on the decl_obstack, we must
   copy it here to keep it from being reclaimed when the decl storage
   is reclaimed.

   IN_DECL, if non-NULL, is the template declaration we are trying to
   instantiate.  

   If ENTERING_SCOPE is non-zero, we are about to enter the scope of
   the class we are looking up.

   If the template class is really a local class in a template
   function, then the FUNCTION_CONTEXT is the function in which it is
   being instantiated.  */

tree
lookup_template_class (d1, arglist, in_decl, context, entering_scope)
     tree d1, arglist;
     tree in_decl;
     tree context;
     int entering_scope;
{
  tree template = NULL_TREE, parmlist;
  tree t;

  if (TREE_CODE (d1) == IDENTIFIER_NODE)
    {
      if (IDENTIFIER_VALUE (d1) 
          && DECL_TEMPLATE_TEMPLATE_PARM_P (IDENTIFIER_VALUE (d1)))
        template = IDENTIFIER_VALUE (d1);
      else
        {
          if (context)
            push_decl_namespace (context);
          if (current_class_type != NULL_TREE)
            template = 
              maybe_get_template_decl_from_type_decl
              (IDENTIFIER_CLASS_VALUE (d1));
          if (template == NULL_TREE)
            template = lookup_name_nonclass (d1);
          if (context)
            pop_decl_namespace ();
        }
      if (template)
        context = DECL_CONTEXT (template);
    }
  else if (TREE_CODE (d1) == TYPE_DECL && IS_AGGR_TYPE (TREE_TYPE (d1)))
    {
      if (CLASSTYPE_TEMPLATE_INFO (TREE_TYPE (d1)))
        {
          template = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (d1));
          d1 = DECL_NAME (template);
        }
    }
  else if (TREE_CODE (d1) == ENUMERAL_TYPE 
           || (TREE_CODE_CLASS (TREE_CODE (d1)) == 't' 
               && IS_AGGR_TYPE (d1)))
    {
      template = TYPE_TI_TEMPLATE (d1);
      d1 = DECL_NAME (template);
    }
  else if (TREE_CODE (d1) == TEMPLATE_DECL
           && TREE_CODE (DECL_RESULT (d1)) == TYPE_DECL)
    {
      template = d1;
      d1 = DECL_NAME (template);
      context = DECL_CONTEXT (template);
    }
  else
    my_friendly_abort (272);

  /* With something like `template <class T> class X class X { ... };'
     we could end up with D1 having nothing but an IDENTIFIER_VALUE.
     We don't want to do that, but we have to deal with the situation,
     so let's give them some syntax errors to chew on instead of a
     crash.  */
  if (! template)
    {
      cp_error ("`%T' is not a template", d1);
      return error_mark_node;
    }

  if (context == NULL_TREE)
    context = global_namespace;

  if (TREE_CODE (template) != TEMPLATE_DECL)
    {
      cp_error ("non-template type `%T' used as a template", d1);
      if (in_decl)
        cp_error_at ("for template declaration `%D'", in_decl);
      return error_mark_node;
    }

  if (DECL_TEMPLATE_TEMPLATE_PARM_P (template))
    {
      /* Create a new TEMPLATE_DECL and TEMPLATE_TEMPLATE_PARM node to store
         template arguments */

      tree parm = copy_template_template_parm (TREE_TYPE (template));
      tree template2 = TYPE_STUB_DECL (parm);
      tree arglist2;

      parmlist = DECL_INNERMOST_TEMPLATE_PARMS (template);

      arglist2 = coerce_template_parms (parmlist, arglist, template, 1, 1);
      if (arglist2 == error_mark_node)
        return error_mark_node;

      arglist2 = copy_to_permanent (arglist2);
      TEMPLATE_TEMPLATE_PARM_TEMPLATE_INFO (parm)
        = perm_tree_cons (template2, arglist2, NULL_TREE);
      TYPE_SIZE (parm) = 0;
      return parm;
    }
  else 
    {
      tree template_type = TREE_TYPE (template);
      tree type_decl;
      tree found = NULL_TREE;
      int arg_depth;
      int parm_depth;
      int is_partial_instantiation;

      template = most_general_template (template);
      parmlist = DECL_TEMPLATE_PARMS (template);
      parm_depth = TMPL_PARMS_DEPTH (parmlist);
      arg_depth = TMPL_ARGS_DEPTH (arglist);

      /* We build up the coerced arguments and such on the
         momentary_obstack.  */
      push_momentary ();

      if (arg_depth == 1 && parm_depth > 1)
        {
          /* We've been given an incomplete set of template arguments.
             For example, given:

               template <class T> struct S1 {
                 template <class U> struct S2 {};
                 template <class U> struct S2<U*> {};
                };
             
             we will be called with an ARGLIST of `U*', but the
             TEMPLATE will be `template <class T> template
             <class U> struct S1<T>::S2'.  We must fill in the missing
             arguments.  */
          my_friendly_assert (context != NULL_TREE, 0);
          while (!IS_AGGR_TYPE_CODE (TREE_CODE (context))
                 && context != global_namespace)
            context = DECL_REAL_CONTEXT (context);

          if (context == global_namespace)
            /* This is bad.  We cannot get enough arguments, even from
               the surrounding context, to resolve this class.  One
               case where this might happen is (illegal) code like:

                   template <class U> 
                   template <class T>
                   struct S { 
                     A(const A<T>& a) {}
                   };  
            
               We should catch this error sooner (at the opening curly
               for `S', but it is better to be safe than sorry here.  */
            {
              cp_error ("invalid use of `%D'", template);
              return error_mark_node;
            }

          arglist = add_to_template_args (TYPE_TI_ARGS (context),
                                          arglist);
          arg_depth = TMPL_ARGS_DEPTH (arglist);
        }

      my_friendly_assert (parm_depth == arg_depth, 0);
      
      /* Calculate the BOUND_ARGS.  These will be the args that are
         actually tsubst'd into the definition to create the
         instantiation.  */
      if (parm_depth > 1)
        {
          /* We have multiple levels of arguments to coerce, at once.  */
          int i;
          int saved_depth = TMPL_ARGS_DEPTH (arglist);

          tree bound_args = make_temp_vec (parm_depth);
          
          for (i = saved_depth,
                 t = DECL_TEMPLATE_PARMS (template); 
               i > 0 && t != NULL_TREE;
               --i, t = TREE_CHAIN (t))
            {
              tree a = coerce_template_parms (TREE_VALUE (t),
                                              arglist, template, 1, 1);
              SET_TMPL_ARGS_LEVEL (bound_args, i, a);

              /* We temporarily reduce the length of the ARGLIST so
                 that coerce_template_parms will see only the arguments
                 corresponding to the template parameters it is
                 examining.  */
              TREE_VEC_LENGTH (arglist)--;
            }

          /* Restore the ARGLIST to its full size.  */
          TREE_VEC_LENGTH (arglist) = saved_depth;

          arglist = bound_args;
        }
      else
        arglist
          = coerce_template_parms (INNERMOST_TEMPLATE_PARMS (parmlist),
                                   innermost_args (arglist),
                                   template, 1, 1);

      if (arglist == error_mark_node)
        /* We were unable to bind the arguments.  */
        return error_mark_node;

      /* In the scope of a template class, explicit references to the
         template class refer to the type of the template, not any
         instantiation of it.  For example, in:
         
           template <class T> class C { void f(C<T>); }

         the `C<T>' is just the same as `C'.  Outside of the
         class, however, such a reference is an instantiation.  */
      if (comp_template_args (TYPE_TI_ARGS (template_type),
                              arglist))
        {
          found = template_type;
          
          if (!entering_scope && PRIMARY_TEMPLATE_P (template))
            {
              tree ctx;
              
              /* Note that we use DECL_CONTEXT, rather than
                 CP_DECL_CONTEXT, so that the termination test is
                 always just `ctx'.  We're not interested in namepace
                 scopes.  */
              for (ctx = current_class_type; 
                   ctx; 
                   ctx = (TREE_CODE_CLASS (TREE_CODE (ctx)) == 't') 
                     ? TYPE_CONTEXT (ctx) : DECL_CONTEXT (ctx))
                if (same_type_p (ctx, template_type))
                  break;
              
              if (!ctx)
                /* We're not in the scope of the class, so the
                   TEMPLATE_TYPE is not the type we want after
                   all.  */
                found = NULL_TREE;
            }
        }
      
      if (!found)
        {
          for (found = DECL_TEMPLATE_INSTANTIATIONS (template);
               found; found = TREE_CHAIN (found))
            if (comp_template_args (TREE_PURPOSE (found), arglist))
              break;

          if (found)
            found = TREE_VALUE (found);
        }
      
      if (found)
        {
          pop_momentary ();
          return found;
        }

      /* Since we didn't find the type, we'll have to create it.
         Since we'll be saving this type on the
         DECL_TEMPLATE_INSTANTIATIONS list, it must be permanent.  */
      push_obstacks (&permanent_obstack, &permanent_obstack);
      
      /* This type is a "partial instantiation" if any of the template
         arguments still inolve template parameters.  Note that we set
         IS_PARTIAL_INSTANTIATION for partial specializations as
         well.  */
      is_partial_instantiation = uses_template_parms (arglist);

      /* Create the type.  */
      if (TREE_CODE (template_type) == ENUMERAL_TYPE)
        {
          if (!is_partial_instantiation)
            t = start_enum (TYPE_IDENTIFIER (template_type));
          else
            /* We don't want to call start_enum for this type, since
               the values for the enumeration constants may involve
               template parameters.  And, no one should be interested
               in the enumeration constants for such a type.  */
            t = make_node (ENUMERAL_TYPE);
        }
      else
        {
          t = make_lang_type (TREE_CODE (template_type));
          CLASSTYPE_DECLARED_CLASS (t) 
            = CLASSTYPE_DECLARED_CLASS (template_type);
          CLASSTYPE_GOT_SEMICOLON (t) = 1;
          SET_CLASSTYPE_IMPLICIT_INSTANTIATION (t);
          TYPE_FOR_JAVA (t) = TYPE_FOR_JAVA (template_type);
        }

      /* If we called start_enum above, this information will already
         be set up.  */
      if (!TYPE_NAME (t))
        {
          TYPE_CONTEXT (t) = FROB_CONTEXT (context);
          
          /* Create a stub TYPE_DECL for it.  */
          type_decl = build_decl (TYPE_DECL, DECL_NAME (template), t);
          SET_DECL_ARTIFICIAL (type_decl);
          DECL_CONTEXT (type_decl) = TYPE_CONTEXT (t);
          DECL_SOURCE_FILE (type_decl) 
            = DECL_SOURCE_FILE (TYPE_STUB_DECL (template_type));
          DECL_SOURCE_LINE (type_decl) 
            = DECL_SOURCE_LINE (TYPE_STUB_DECL (template_type));
          TYPE_STUB_DECL (t) = TYPE_NAME (t) = type_decl;
        }
      else
        type_decl = TYPE_NAME (t);

      /* Set up the template information.  We have to figure out which
         template is the immediate parent if this is a full
         instantiation.  */
      if (parm_depth == 1 || is_partial_instantiation
          || !PRIMARY_TEMPLATE_P (template))
        /* This case is easy; there are no member templates involved.  */
        found = template;
      else
        {
          /* This is a full instantiation of a member template.  There
             should be some partial instantiation of which this is an
             instance.  */

          for (found = DECL_TEMPLATE_INSTANTIATIONS (template);
               found; found = TREE_CHAIN (found))
            {
              int success;
              tree tmpl = CLASSTYPE_TI_TEMPLATE (TREE_VALUE (found));

              /* We only want partial instantiations, here, not
                 specializations or full instantiations.  */
              if (CLASSTYPE_TEMPLATE_SPECIALIZATION (TREE_VALUE (found))
                  || !uses_template_parms (TREE_VALUE (found)))
                continue;

              /* Temporarily reduce by one the number of levels in the
                 ARGLIST and in FOUND so as to avoid comparing the
                 last set of arguments.  */
              TREE_VEC_LENGTH (arglist)--;
              TREE_VEC_LENGTH (TREE_PURPOSE (found)) --;

              /* See if the arguments match.  If they do, then TMPL is
                 the partial instantiation we want.  */
              success = comp_template_args (TREE_PURPOSE (found), arglist);

              /* Restore the argument vectors to their full size.  */
              TREE_VEC_LENGTH (arglist)++;
              TREE_VEC_LENGTH (TREE_PURPOSE (found))++;

              if (success)
                {
                  found = tmpl;
                  break;
                }
            }

          if (!found)
            my_friendly_abort (0);
        }

      arglist = copy_to_permanent (arglist);
      SET_TYPE_TEMPLATE_INFO (t,
                              tree_cons (found, arglist, NULL_TREE));  
      DECL_TEMPLATE_INSTANTIATIONS (template) 
        = tree_cons (arglist, t, 
                     DECL_TEMPLATE_INSTANTIATIONS (template));

      if (TREE_CODE (t) == ENUMERAL_TYPE 
          && !is_partial_instantiation)
        /* Now that the type has been registered on the instantiations
           list, we set up the enumerators.  Because the enumeration
           constants may involve the enumeration type itself, we make
           sure to register the type first, and then create the
           constants.  That way, doing tsubst_expr for the enumeration
           constants won't result in recursive calls here; we'll find
           the instantiation and exit above.  */
        tsubst_enum (template_type, t, arglist);

      /* We're done with the permanent obstack, now.  */
      pop_obstacks ();
      /* We're also done with the momentary allocation we started
         above.  */
      pop_momentary ();

      /* Reset the name of the type, now that CLASSTYPE_TEMPLATE_INFO
         is set up.  */
      if (TREE_CODE (t) != ENUMERAL_TYPE)
        DECL_NAME (type_decl) = classtype_mangled_name (t);
      DECL_ASSEMBLER_NAME (type_decl) = DECL_NAME (type_decl);
      if (!is_partial_instantiation)
        {
          DECL_ASSEMBLER_NAME (type_decl)
            = get_identifier (build_overload_name (t, 1, 1));

          /* For backwards compatibility; code that uses
             -fexternal-templates expects looking up a template to
             instantiate it.  I think DDD still relies on this.
             (jason 8/20/1998) */
          if (TREE_CODE (t) != ENUMERAL_TYPE
              && flag_external_templates
              && CLASSTYPE_INTERFACE_KNOWN (TREE_TYPE (template))
              && ! CLASSTYPE_INTERFACE_ONLY (TREE_TYPE (template)))
            add_pending_template (t);
        }
      else
        /* If the type makes use of template parameters, the
           code that generates debugging information will crash.  */
        DECL_IGNORED_P (TYPE_STUB_DECL (t)) = 1;

      return t;
    }
}
\f
/* For each TEMPLATE_TYPE_PARM, TEMPLATE_TEMPLATE_PARM, or
   TEMPLATE_PARM_INDEX in T, call FN with the parameter and the DATA.
   If FN returns non-zero, the iteration is terminated, and
   for_each_template_parm returns 1.  Otherwise, the iteration
   continues.  If FN never returns a non-zero value, the value
   returned by for_each_template_parm is 0.  If FN is NULL, it is
   considered to be the function which always returns 1.  */

static int
for_each_template_parm (t, fn, data)
     tree t;
     tree_fn_t fn;
     void* data;
{
  if (!t)
    return 0;

  if (TREE_CODE_CLASS (TREE_CODE (t)) == 't'
      && for_each_template_parm (TYPE_CONTEXT (t), fn, data))
    return 1;

  switch (TREE_CODE (t))
    {
    case INDIRECT_REF:
    case COMPONENT_REF:
      /* We assume that the object must be instantiated in order to build
         the COMPONENT_REF, so we test only whether the type of the
         COMPONENT_REF uses template parms.  */
      return for_each_template_parm (TREE_TYPE (t), fn, data);

    case ARRAY_REF:
      return (for_each_template_parm (TREE_OPERAND (t, 0), fn, data)
              || for_each_template_parm (TREE_OPERAND (t, 1), fn, data));

    case IDENTIFIER_NODE:
      if (!IDENTIFIER_TEMPLATE (t))
        return 0;
      my_friendly_abort (42);

      /* aggregates of tree nodes */
    case TREE_VEC:
      {
        int i = TREE_VEC_LENGTH (t);
        while (i--)
          if (for_each_template_parm (TREE_VEC_ELT (t, i), fn, data))
            return 1;
        return 0;
      }
    case TREE_LIST:
      if (for_each_template_parm (TREE_PURPOSE (t), fn, data)
          || for_each_template_parm (TREE_VALUE (t), fn, data))
        return 1;
      return for_each_template_parm (TREE_CHAIN (t), fn, data);

    case OVERLOAD:
      if (for_each_template_parm (OVL_FUNCTION (t), fn, data))
        return 1;
      return for_each_template_parm (OVL_CHAIN (t), fn, data);

      /* constructed type nodes */
    case POINTER_TYPE:
    case REFERENCE_TYPE:
      return for_each_template_parm (TREE_TYPE (t), fn, data);

    case RECORD_TYPE:
      if (TYPE_PTRMEMFUNC_FLAG (t))
        return for_each_template_parm (TYPE_PTRMEMFUNC_FN_TYPE (t),
                                       fn, data);
      /* Fall through.  */

    case UNION_TYPE:
    case ENUMERAL_TYPE:
      if (! TYPE_TEMPLATE_INFO (t))
        return 0;
      return for_each_template_parm (TREE_VALUE
                                     (TYPE_TEMPLATE_INFO (t)),
                                     fn, data);
    case METHOD_TYPE:
      if (for_each_template_parm (TYPE_METHOD_BASETYPE (t), fn, data))
        return 1;
      /* Fall through.  */

    case FUNCTION_TYPE:
      /* Check the parameter types.  Since default arguments are not
         instantiated until they are needed, the TYPE_ARG_TYPES may
         contain expressions that involve template parameters.  But,
         no-one should be looking at them yet.  And, once they're
         instantiated, they don't contain template parameters, so
         there's no point in looking at them then, either.  */
      {
        tree parm;

        for (parm = TYPE_ARG_TYPES (t); parm; parm = TREE_CHAIN (parm))
          if (for_each_template_parm (TREE_VALUE (parm), fn, data))
            return 1;
      }

      /* Check the return type, too.  */
      return for_each_template_parm (TREE_TYPE (t), fn, data);

    case ARRAY_TYPE:
      if (for_each_template_parm (TYPE_DOMAIN (t), fn, data))
        return 1;
      return for_each_template_parm (TREE_TYPE (t), fn, data);
    case OFFSET_TYPE:
      if (for_each_template_parm (TYPE_OFFSET_BASETYPE (t), fn, data))
        return 1;
      return for_each_template_parm (TREE_TYPE (t), fn, data);

      /* decl nodes */
    case TYPE_DECL:
      return for_each_template_parm (TREE_TYPE (t), fn, data);

    case TEMPLATE_DECL:
      /* A template template parameter is encountered */
      if (DECL_TEMPLATE_TEMPLATE_PARM_P (t))
        return for_each_template_parm (TREE_TYPE (t), fn, data);
      /* Already substituted template template parameter */
      return 0;
      
    case CONST_DECL:
      if (for_each_template_parm (DECL_INITIAL (t), fn, data))
        return 1;
      goto check_type_and_context;

    case FUNCTION_DECL:
    case VAR_DECL:
      /* ??? What about FIELD_DECLs?  */
      if (DECL_LANG_SPECIFIC (t) && DECL_TEMPLATE_INFO (t)
          && for_each_template_parm (DECL_TI_ARGS (t), fn, data))
        return 1;
      /* fall through */
    case PARM_DECL:
    check_type_and_context:
      if (for_each_template_parm (TREE_TYPE (t), fn, data))
        return 1;
      if (DECL_CONTEXT (t) 
          && for_each_template_parm (DECL_CONTEXT (t), fn, data))
        return 1;
      return 0;

    case CALL_EXPR:
      return (for_each_template_parm (TREE_OPERAND (t, 0), fn, data)
              || for_each_template_parm (TREE_OPERAND (t, 1), fn, data));
        
    case ADDR_EXPR:
      return for_each_template_parm (TREE_OPERAND (t, 0), fn, data);

      /* template parm nodes */
    case TEMPLATE_TEMPLATE_PARM:
      /* Record template parameters such as `T' inside `TT<T>'.  */
      if (TEMPLATE_TEMPLATE_PARM_TEMPLATE_INFO (t)
          && for_each_template_parm (TYPE_TI_ARGS (t), fn, data))
        return 1;
    case TEMPLATE_TYPE_PARM:
    case TEMPLATE_PARM_INDEX:
      if (fn)
        return (*fn)(t, data);
      else
        return 1;

      /* simple type nodes */
    case INTEGER_TYPE:
      if (for_each_template_parm (TYPE_MIN_VALUE (t), fn, data))
        return 1;
      return for_each_template_parm (TYPE_MAX_VALUE (t), fn, data);

    case REAL_TYPE:
    case COMPLEX_TYPE:
    case VOID_TYPE:
    case BOOLEAN_TYPE:
    case NAMESPACE_DECL:
      return 0;

      /* constants */
    case INTEGER_CST:
    case REAL_CST:
    case STRING_CST:
      return 0;

    case ERROR_MARK:
      /* Non-error_mark_node ERROR_MARKs are bad things.  */
      my_friendly_assert (t == error_mark_node, 274);
      /* NOTREACHED */
      return 0;

    case LOOKUP_EXPR:
    case TYPENAME_TYPE:
      return 1;

    case PTRMEM_CST:
      return for_each_template_parm (TREE_TYPE (t), fn, data);

    case SCOPE_REF:
      return for_each_template_parm (TREE_OPERAND (t, 0), fn, data);

    case CONSTRUCTOR:
      if (TREE_TYPE (t) && TYPE_PTRMEMFUNC_P (TREE_TYPE (t)))
        return for_each_template_parm (TYPE_PTRMEMFUNC_FN_TYPE
                                       (TREE_TYPE (t)), fn, data);
      return for_each_template_parm (TREE_OPERAND (t, 1), fn, data);

    case MODOP_EXPR:
    case CAST_EXPR:
    case REINTERPRET_CAST_EXPR:
    case CONST_CAST_EXPR:
    case STATIC_CAST_EXPR:
    case DYNAMIC_CAST_EXPR:
    case ARROW_EXPR:
    case DOTSTAR_EXPR:
    case TYPEID_EXPR:
      return 1;

    case SIZEOF_EXPR:
    case ALIGNOF_EXPR:
      return for_each_template_parm (TREE_OPERAND (t, 0), fn, data);

    default:
      switch (TREE_CODE_CLASS (TREE_CODE (t)))
        {
        case '1':
        case '2':
        case 'e':
        case '<':
          {
            int i;
            for (i = first_rtl_op (TREE_CODE (t)); --i >= 0;)
              if (for_each_template_parm (TREE_OPERAND (t, i), fn, data))
                return 1;
            return 0;
          }
        default:
          break;
        }
      sorry ("testing %s for template parms",
             tree_code_name [(int) TREE_CODE (t)]);
      my_friendly_abort (82);
      /* NOTREACHED */
      return 0;
    }
}

int
uses_template_parms (t)
     tree t;
{
  return for_each_template_parm (t, 0, 0);
}

static struct tinst_level *current_tinst_level;
static struct tinst_level *free_tinst_level;
static int tinst_depth;
extern int max_tinst_depth;
#ifdef GATHER_STATISTICS
int depth_reached;
#endif
int tinst_level_tick;
int last_template_error_tick;

/* Print out all the template instantiations that we are currently
   working on.  If ERR, we are being called from cp_thing, so do
   the right thing for an error message.  */

static void
print_template_context (err)
     int err;
{
  struct tinst_level *p = current_tinst_level;
  int line = lineno;
  char *file = input_filename;

  if (err && p)
    {
      if (current_function_decl != p->decl
          && current_function_decl != NULL_TREE)
        /* We can get here during the processing of some synthesized
           method.  Then, p->decl will be the function that's causing
           the synthesis.  */
        ;
      else
        {
          if (current_function_decl == p->decl)
            /* Avoid redundancy with the the "In function" line.  */;
          else 
            fprintf (stderr, "%s: In instantiation of `%s':\n",
                     file, decl_as_string (p->decl, 0));
          
          line = p->line;
          file = p->file;
          p = p->next;
        }
    }

  for (; p; p = p->next)
    {
      fprintf (stderr, "%s:%d:   instantiated from `%s'\n", file, line,
               decl_as_string (p->decl, 0));
      line = p->line;
      file = p->file;
    }
  fprintf (stderr, "%s:%d:   instantiated from here\n", file, line);
}

/* Called from cp_thing to print the template context for an error.  */

void
maybe_print_template_context ()
{
  if (last_template_error_tick == tinst_level_tick
      || current_tinst_level == 0)
    return;

  last_template_error_tick = tinst_level_tick;
  print_template_context (1);
}

static int
push_tinst_level (d)
     tree d;
{
  struct tinst_level *new;

  if (tinst_depth >= max_tinst_depth)
    {
      /* If the instantiation in question still has unbound template parms,
         we don't really care if we can't instantiate it, so just return.
         This happens with base instantiation for implicit `typename'.  */
      if (uses_template_parms (d))
        return 0;

      last_template_error_tick = tinst_level_tick;
      error ("template instantiation depth exceeds maximum of %d",
             max_tinst_depth);
      error (" (use -ftemplate-depth-NN to increase the maximum)");
      cp_error ("  instantiating `%D'", d);

      print_template_context (0);

      return 0;
    }

  if (free_tinst_level)
    {
      new = free_tinst_level;
      free_tinst_level = new->next;
    }
  else
    new = (struct tinst_level *) xmalloc (sizeof (struct tinst_level));

  new->decl = d;
  new->line = lineno;
  new->file = input_filename;
  new->next = current_tinst_level;
  current_tinst_level = new;

  ++tinst_depth;
#ifdef GATHER_STATISTICS
  if (tinst_depth > depth_reached)
    depth_reached = tinst_depth;
#endif

  ++tinst_level_tick;
  return 1;
}

void
pop_tinst_level ()
{
  struct tinst_level *old = current_tinst_level;

  /* Restore the filename and line number stashed away when we started
     this instantiation.  */
  lineno = old->line;
  input_filename = old->file;
  extract_interface_info ();
  
  current_tinst_level = old->next;
  old->next = free_tinst_level;
  free_tinst_level = old;
  --tinst_depth;
  ++tinst_level_tick;
}

struct tinst_level *
tinst_for_decl ()
{
  struct tinst_level *p = current_tinst_level;

  if (p)
    for (; p->next ; p = p->next )
      ;
  return p;
}

/* DECL is a friend FUNCTION_DECL or TEMPLATE_DECL.  ARGS is the
   vector of template arguments, as for tsubst.

   Returns an appropriate tsbust'd friend declaration.  */

static tree
tsubst_friend_function (decl, args)
     tree decl;
     tree args;
{
  tree new_friend;
  int line = lineno;
  char *file = input_filename;

  lineno = DECL_SOURCE_LINE (decl);
  input_filename = DECL_SOURCE_FILE (decl);

  if (TREE_CODE (decl) == FUNCTION_DECL 
      && DECL_TEMPLATE_INSTANTIATION (decl)
      && TREE_CODE (DECL_TI_TEMPLATE (decl)) != TEMPLATE_DECL)
    /* This was a friend declared with an explicit template
       argument list, e.g.:
       
       friend void f<>(T);
       
       to indicate that f was a template instantiation, not a new
       function declaration.  Now, we have to figure out what
       instantiation of what template.  */
    {
      tree template_id;
      tree new_args;
      tree tmpl;

      template_id
        = lookup_template_function (tsubst_expr (DECL_TI_TEMPLATE (decl),
                                                 args, /*complain=*/1, 
                                                 NULL_TREE),
                                    tsubst (DECL_TI_ARGS (decl),
                                            args, /*complain=*/1, 
                                            NULL_TREE));
      /* FIXME: The decl we create via the next tsubst could be
         created on a temporary obstack.  */
      new_friend = tsubst (decl, args, /*complain=*/1, NULL_TREE);
      tmpl = determine_specialization (template_id, new_friend,
                                       &new_args, 
                                       /*need_member_template=*/0);
      new_friend = instantiate_template (tmpl, new_args);
      goto done;
    }

  new_friend = tsubst (decl, args, /*complain=*/1, NULL_TREE);
        
  /* The NEW_FRIEND will look like an instantiation, to the
     compiler, but is not an instantiation from the point of view of
     the language.  For example, we might have had:
     
     template <class T> struct S {
       template <class U> friend void f(T, U);
     };
     
     Then, in S<int>, template <class U> void f(int, U) is not an
     instantiation of anything.  */
  DECL_USE_TEMPLATE (new_friend) = 0;
  if (TREE_CODE (decl) == TEMPLATE_DECL)
    DECL_USE_TEMPLATE (DECL_TEMPLATE_RESULT (new_friend)) = 0;

  /* The mangled name for the NEW_FRIEND is incorrect.  The call to
     tsubst will have resulted in a call to
     set_mangled_name_for_template_decl.  But, the function is not a
     template instantiation and should not be mangled like one.
     Therefore, we remangle the function name.  We don't have to do
     this if the NEW_FRIEND is a template since
     set_mangled_name_for_template_decl doesn't do anything if the
     function declaration still uses template arguments.  */
  if (TREE_CODE (new_friend) != TEMPLATE_DECL)
    {
      set_mangled_name_for_decl (new_friend);
      DECL_RTL (new_friend) = 0;
      make_decl_rtl (new_friend, NULL_PTR, 1);
    }
      
  if (DECL_NAMESPACE_SCOPE_P (new_friend))
    {
      tree old_decl;
      tree new_friend_template_info;
      tree new_friend_result_template_info;
      int  new_friend_is_defn;

      /* We must save some information from NEW_FRIEND before calling
         duplicate decls since that function will free NEW_FRIEND if
         possible.  */
      new_friend_template_info = DECL_TEMPLATE_INFO (new_friend);
      if (TREE_CODE (new_friend) == TEMPLATE_DECL)
        {
          /* This declaration is a `primary' template.  */
          DECL_PRIMARY_TEMPLATE (new_friend) = new_friend;
          
          new_friend_is_defn 
            = DECL_INITIAL (DECL_RESULT (new_friend)) != NULL_TREE;
          new_friend_result_template_info
            = DECL_TEMPLATE_INFO (DECL_RESULT (new_friend));
        }
      else
        {
          new_friend_is_defn = DECL_INITIAL (new_friend) != NULL_TREE;
          new_friend_result_template_info = NULL_TREE;
        }

      old_decl = pushdecl_namespace_level (new_friend);

      if (old_decl != new_friend)
        {
          /* This new friend declaration matched an existing
             declaration.  For example, given:

               template <class T> void f(T);
               template <class U> class C { 
                 template <class T> friend void f(T) {} 
               };

             the friend declaration actually provides the definition
             of `f', once C has been instantiated for some type.  So,
             old_decl will be the out-of-class template declaration,
             while new_friend is the in-class definition.

             But, if `f' was called before this point, the
             instantiation of `f' will have DECL_TI_ARGS corresponding
             to `T' but not to `U', references to which might appear
             in the definition of `f'.  Previously, the most general
             template for an instantiation of `f' was the out-of-class
             version; now it is the in-class version.  Therefore, we
             run through all specialization of `f', adding to their
             DECL_TI_ARGS appropriately.  In particular, they need a
             new set of outer arguments, corresponding to the
             arguments for this class instantiation.  

             The same situation can arise with something like this:

               friend void f(int);
               template <class T> class C { 
                 friend void f(T) {}
               };

             when `C<int>' is instantiated.  Now, `f(int)' is defined
             in the class.  */

          if (!new_friend_is_defn)
            /* On the other hand, if the in-class declaration does
               *not* provide a definition, then we don't want to alter
               existing definitions.  We can just leave everything
               alone.  */
            ;
          else
            {
              /* Overwrite whatever template info was there before, if
                 any, with the new template information pertaining to
                 the declaration.  */
              DECL_TEMPLATE_INFO (old_decl) = new_friend_template_info;

              if (TREE_CODE (old_decl) != TEMPLATE_DECL)
                /* duplicate_decls will take care of this case.  */
                ;
              else 
                {
                  tree t;
                  tree new_friend_args;

                  DECL_TEMPLATE_INFO (DECL_RESULT (old_decl)) 
                    = new_friend_result_template_info;
                    
                  new_friend_args = TI_ARGS (new_friend_template_info);
                  for (t = DECL_TEMPLATE_SPECIALIZATIONS (old_decl); 
                       t != NULL_TREE;
                       t = TREE_CHAIN (t))
                    {
                      tree spec = TREE_VALUE (t);
                  
                      DECL_TI_ARGS (spec) 
                        = add_outermost_template_args (new_friend_args,
                                                       DECL_TI_ARGS (spec));
                      DECL_TI_ARGS (spec)
                        = copy_to_permanent (DECL_TI_ARGS (spec));
                    }

                  /* Now, since specializations are always supposed to
                     hang off of the most general template, we must move
                     them.  */
                  t = most_general_template (old_decl);
                  if (t != old_decl)
                    {
                      DECL_TEMPLATE_SPECIALIZATIONS (t)
                        = chainon (DECL_TEMPLATE_SPECIALIZATIONS (t),
                                   DECL_TEMPLATE_SPECIALIZATIONS (old_decl));
                      DECL_TEMPLATE_SPECIALIZATIONS (old_decl) = NULL_TREE;
                    }
                }
            }

          /* The information from NEW_FRIEND has been merged into OLD_DECL
             by duplicate_decls.  */
          new_friend = old_decl;
        }
    }
  else if (TYPE_SIZE (DECL_CONTEXT (new_friend)))
    {
      /* Check to see that the declaration is really present, and,
         possibly obtain an improved declaration.  */
      tree fn = check_classfn (DECL_CONTEXT (new_friend),
                               new_friend);
      
      if (fn)
        new_friend = fn;
    }

 done:
  lineno = line;
  input_filename = file;
  return new_friend;
}

/* FRIEND_TMPL is a friend TEMPLATE_DECL.  ARGS is the vector of
   template arguments, as for tsubst.

   Returns an appropriate tsbust'd friend type.  */

static tree
tsubst_friend_class (friend_tmpl, args)
     tree friend_tmpl;
     tree args;
{
  tree friend_type;
  tree tmpl = lookup_name (DECL_NAME (friend_tmpl), 1); 

  tmpl = maybe_get_template_decl_from_type_decl (tmpl);

  if (tmpl != NULL_TREE && DECL_CLASS_TEMPLATE_P (tmpl))
    {
      /* The friend template has already been declared.  Just
         check to see that the declarations match, and install any new
         default parameters.  We must tsubst the default parameters,
         of course.  We only need the innermost template parameters
         because that is all that redeclare_class_template will look
         at.  */
      tree parms 
        = tsubst_template_parms (DECL_TEMPLATE_PARMS (friend_tmpl),
                                 args, /*complain=*/1);
      redeclare_class_template (TREE_TYPE (tmpl), parms);
      friend_type = TREE_TYPE (tmpl);
    }
  else
    {
      /* The friend template has not already been declared.  In this
         case, the instantiation of the template class will cause the
         injection of this template into the global scope.  */
      tmpl = tsubst (friend_tmpl, args, /*complain=*/1, NULL_TREE);

      /* The new TMPL is not an instantiation of anything, so we
         forget its origins.  We don't reset CLASSTYPE_TI_TEMPLATE for
         the new type because that is supposed to be the corresponding
         template decl, i.e., TMPL.  */
      DECL_USE_TEMPLATE (tmpl) = 0;
      DECL_TEMPLATE_INFO (tmpl) = NULL_TREE;
      CLASSTYPE_USE_TEMPLATE (TREE_TYPE (tmpl)) = 0;

      /* Inject this template into the global scope.  */
      friend_type = TREE_TYPE (pushdecl_top_level (tmpl));
    }

  return friend_type;
}

tree
instantiate_class_template (type)
     tree type;
{
  tree template, args, pattern, t;
  tree typedecl;

  if (type == error_mark_node)
    return error_mark_node;

  if (TYPE_BEING_DEFINED (type) || TYPE_SIZE (type))
    return type;

  /* We want to allocate temporary vectors of template arguments and
     template argument expressions on the momentary obstack, not on
     the expression obstack.  Otherwise, all the space allocated in
     argument coercion and such is simply lost.  */
  push_momentary ();

  /* Figure out which template is being instantiated.  */
  template = most_general_template (CLASSTYPE_TI_TEMPLATE (type));
  my_friendly_assert (TREE_CODE (template) == TEMPLATE_DECL, 279);

  /* Figure out which arguments are being used to do the
     instantiation.  */
  args = CLASSTYPE_TI_ARGS (type);
  PARTIAL_INSTANTIATION_P (type) = uses_template_parms (args);

  if (pedantic && PARTIAL_INSTANTIATION_P (type))
    /* If this is a partial instantiation, then we can't instantiate
       the type; there's no telling whether or not one of the
       template parameters might eventually be instantiated to some
       value that results in a specialization being used.  For
       example, consider:

         template <class T>
         struct S {};

         template <class U> 
         void f(S<U>);
             
         template <> 
         struct S<int> {};

       Now, the `S<U>' in `f<int>' is the specialization, not an
       instantiation of the original template.  */
    goto end;

  /* Determine what specialization of the original template to
     instantiate.  */
  if (PARTIAL_INSTANTIATION_P (type))
    /* There's no telling which specialization is appropriate at this
       point.  Since all peeking at the innards of this partial
       instantiation are extensions (like the "implicit typename"
       extension, which allows users to omit the keyword `typename' on
       names that are declared as types in template base classes), we
       are free to do what we please.

       Trying to figure out which partial instantiation to use can
       cause a crash.  (Some of the template arguments don't even have
       types.)  So, we just use the most general version.  */
    t = NULL_TREE;
  else
    {
      t = most_specialized_class (template, args);

      if (t == error_mark_node)
        {
          char *str = "candidates are:";
          cp_error ("ambiguous class template instantiation for `%#T'", type);
          for (t = DECL_TEMPLATE_SPECIALIZATIONS (template); t; 
               t = TREE_CHAIN (t))
            {
              if (get_class_bindings (TREE_VALUE (t), TREE_PURPOSE (t),
                                      args))
                {
                  cp_error_at ("%s %+#T", str, TREE_TYPE (t));
                  str = "               ";
                }
            }
          TYPE_BEING_DEFINED (type) = 1;
          type = error_mark_node;
          goto end;
        }
    }

  if (t)
    pattern = TREE_TYPE (t);
  else
    pattern = TREE_TYPE (template);

  /* If the template we're instantiating is incomplete, then clearly
     there's nothing we can do.  */
  if (TYPE_SIZE (pattern) == NULL_TREE)
    goto end;

  /* If this is a partial instantiation, don't tsubst anything.  We will
     only use this type for implicit typename, so the actual contents don't
     matter.  All that matters is whether a particular name is a type.  */
  if (PARTIAL_INSTANTIATION_P (type))
    {
      /* The fields set here must be kept in sync with those cleared
         in begin_class_definition.  */
      TYPE_BINFO_BASETYPES (type) = TYPE_BINFO_BASETYPES (pattern);
      TYPE_FIELDS (type) = TYPE_FIELDS (pattern);
      TYPE_METHODS (type) = TYPE_METHODS (pattern);
      CLASSTYPE_TAGS (type) = CLASSTYPE_TAGS (pattern);
      /* Pretend that the type is complete, so that we will look
         inside it during name lookup and such.  */
      TYPE_SIZE (type) = integer_zero_node;
      goto end;
    }

  /* If we've recursively instantiated too many templates, stop.  */
  if (! push_tinst_level (type))
    goto end;

  /* Now we're really doing the instantiation.  Mark the type as in
     the process of being defined.  */
  TYPE_BEING_DEFINED (type) = 1;

  maybe_push_to_top_level (uses_template_parms (type));
  pushclass (type, 0);

  if (t)
    {
      /* This TYPE is actually a instantiation of of a partial
         specialization.  We replace the innermost set of ARGS with
         the arguments appropriate for substitution.  For example,
         given:

           template <class T> struct S {};
           template <class T> struct S<T*> {};
         
         and supposing that we are instantiating S<int*>, ARGS will
         present be {int*} but we need {int}.  */
      tree inner_args 
        = get_class_bindings (TREE_VALUE (t), TREE_PURPOSE (t),
                              args);

      /* If there were multiple levels in ARGS, replacing the
         innermost level would alter CLASSTYPE_TI_ARGS, which we don't
         want, so we make a copy first.  */
      if (TMPL_ARGS_HAVE_MULTIPLE_LEVELS (args))
        {
          args = copy_node (args);
          SET_TMPL_ARGS_LEVEL (args, TMPL_ARGS_DEPTH (args), inner_args);
        }
      else
        args = inner_args;
    }

  if (flag_external_templates)
    {
      if (flag_alt_external_templates)
        {
          CLASSTYPE_INTERFACE_ONLY (type) = interface_only;
          SET_CLASSTYPE_INTERFACE_UNKNOWN_X (type, interface_unknown);
          CLASSTYPE_VTABLE_NEEDS_WRITING (type)
            = (! CLASSTYPE_INTERFACE_ONLY (type)
               && CLASSTYPE_INTERFACE_KNOWN (type));
        }
      else
        {
          CLASSTYPE_INTERFACE_ONLY (type) = CLASSTYPE_INTERFACE_ONLY (pattern);
          SET_CLASSTYPE_INTERFACE_UNKNOWN_X
            (type, CLASSTYPE_INTERFACE_UNKNOWN (pattern));
          CLASSTYPE_VTABLE_NEEDS_WRITING (type)
            = (! CLASSTYPE_INTERFACE_ONLY (type)
               && CLASSTYPE_INTERFACE_KNOWN (type));
        }
    }
  else
    {
      SET_CLASSTYPE_INTERFACE_UNKNOWN (type);
      CLASSTYPE_VTABLE_NEEDS_WRITING (type) = 1;
    }

  TYPE_HAS_CONSTRUCTOR (type) = TYPE_HAS_CONSTRUCTOR (pattern);
  TYPE_HAS_DESTRUCTOR (type) = TYPE_HAS_DESTRUCTOR (pattern);
  TYPE_HAS_ASSIGNMENT (type) = TYPE_HAS_ASSIGNMENT (pattern);
  TYPE_OVERLOADS_CALL_EXPR (type) = TYPE_OVERLOADS_CALL_EXPR (pattern);
  TYPE_OVERLOADS_ARRAY_REF (type) = TYPE_OVERLOADS_ARRAY_REF (pattern);
  TYPE_OVERLOADS_ARROW (type) = TYPE_OVERLOADS_ARROW (pattern);
  TYPE_GETS_NEW (type) = TYPE_GETS_NEW (pattern);
  TYPE_GETS_DELETE (type) = TYPE_GETS_DELETE (pattern);
  TYPE_VEC_DELETE_TAKES_SIZE (type) = TYPE_VEC_DELETE_TAKES_SIZE (pattern);
  TYPE_HAS_ASSIGN_REF (type) = TYPE_HAS_ASSIGN_REF (pattern);
  TYPE_HAS_CONST_ASSIGN_REF (type) = TYPE_HAS_CONST_ASSIGN_REF (pattern);
  TYPE_HAS_ABSTRACT_ASSIGN_REF (type) = TYPE_HAS_ABSTRACT_ASSIGN_REF (pattern);
  TYPE_HAS_INIT_REF (type) = TYPE_HAS_INIT_REF (pattern);
  TYPE_HAS_CONST_INIT_REF (type) = TYPE_HAS_CONST_INIT_REF (pattern);
  TYPE_HAS_DEFAULT_CONSTRUCTOR (type) = TYPE_HAS_DEFAULT_CONSTRUCTOR (pattern);
  TYPE_HAS_CONVERSION (type) = TYPE_HAS_CONVERSION (pattern);
  TYPE_USES_COMPLEX_INHERITANCE (type)
    = TYPE_USES_COMPLEX_INHERITANCE (pattern);
  TYPE_USES_MULTIPLE_INHERITANCE (type)
    = TYPE_USES_MULTIPLE_INHERITANCE (pattern);
  TYPE_USES_VIRTUAL_BASECLASSES (type)
    = TYPE_USES_VIRTUAL_BASECLASSES (pattern);
  TYPE_PACKED (type) = TYPE_PACKED (pattern);
  TYPE_ALIGN (type) = TYPE_ALIGN (pattern);
  TYPE_FOR_JAVA (type) = TYPE_FOR_JAVA (pattern); /* For libjava's JArray<T> */

  /* We must copy the arguments to the permanent obstack since
     during the tsubst'ing below they may wind up in the
     DECL_TI_ARGS of some instantiated member template.  */
  args = copy_to_permanent (args);

  if (TYPE_BINFO_BASETYPES (pattern))
    {
      tree base_list = NULL_TREE;
      tree pbases = TYPE_BINFO_BASETYPES (pattern);
      int i;

      /* Substitute into each of the bases to determine the actual
         basetypes.  */
      for (i = 0; i < TREE_VEC_LENGTH (pbases); ++i)
        {
          tree base;
          tree access;
          tree pbase;

          pbase = TREE_VEC_ELT (pbases, i);

          /* Substitue to figure out the base class.  */
          base = tsubst (BINFO_TYPE (pbase), args, 
                         /*complain=*/1, NULL_TREE);
          if (base == error_mark_node)
            continue;

          /* Calculate the correct access node.  */
          if (TREE_VIA_VIRTUAL (pbase)) 
            {
              if (TREE_VIA_PUBLIC (pbase))
                access = access_public_virtual_node;
              else if (TREE_VIA_PROTECTED (pbase))
                access = access_protected_virtual_node;
              else 
                access = access_private_virtual_node;
            }
          else
            {
              if (TREE_VIA_PUBLIC (pbase))
                access = access_public_node;
              else if (TREE_VIA_PROTECTED (pbase))
                access = access_protected_node;
              else 
                access = access_private_node;
            }

          base_list = tree_cons (access, base, base_list);
        }

      /* The list is now in reverse order; correct that.  */
      base_list = nreverse (base_list);

      /* Now call xref_basetypes to set up all the base-class
         information.  */
      xref_basetypes (TREE_CODE (pattern) == RECORD_TYPE
                      ? (CLASSTYPE_DECLARED_CLASS (pattern)
                         ? class_type_node : record_type_node)
                      : union_type_node,
                      DECL_NAME (TYPE_NAME (pattern)),
                      type,
                      base_list);
    }

  for (t = CLASSTYPE_TAGS (pattern); t; t = TREE_CHAIN (t))
    {
      tree tag = TREE_VALUE (t);
      tree name = TYPE_IDENTIFIER (tag);
      tree newtag;

      newtag = tsubst (tag, args, /*complain=*/1, NULL_TREE);
      if (TREE_CODE (newtag) != ENUMERAL_TYPE)
        {
          if (TYPE_LANG_SPECIFIC (tag) && CLASSTYPE_IS_TEMPLATE (tag))
            /* Unfortunately, lookup_template_class sets
               CLASSTYPE_IMPLICIT_INSTANTIATION for a partial
               instantiation (i.e., for the type of a member template
               class nested within a template class.)  This behavior is
               required for maybe_process_partial_specialization to work
               correctly, but is not accurate in this case; the TAG is not
               an instantiation of anything.  (The corresponding
               TEMPLATE_DECL is an instantiation, but the TYPE is not.) */
            CLASSTYPE_USE_TEMPLATE (newtag) = 0;

          /* Now, we call pushtag to put this NEWTAG into the scope of
             TYPE.  We first set up the IDENTIFIER_TYPE_VALUE to avoid
             pushtag calling push_template_decl.  We don't have to do
             this for enums because it will already have been done in
             tsubst_enum.  */
          if (name)
            SET_IDENTIFIER_TYPE_VALUE (name, newtag);
          pushtag (name, newtag, /*globalize=*/0);
        }
    }

  /* Don't replace enum constants here.  */
  for (t = TYPE_FIELDS (pattern); t; t = TREE_CHAIN (t))
    if (TREE_CODE (t) != CONST_DECL)
      {
        tree r;

        /* The the file and line for this declaration, to assist in
           error message reporting.  Since we called push_tinst_level
           above, we don't need to restore these.  */
        lineno = DECL_SOURCE_LINE (t);
        input_filename = DECL_SOURCE_FILE (t);

        r = tsubst (t, args, /*complain=*/1, NULL_TREE);
        if (TREE_CODE (r) == VAR_DECL)
          {
            pending_statics = perm_tree_cons (NULL_TREE, r, pending_statics);
            /* Perhaps we should do more of grokfield here.  */
            if (DECL_DEFINED_IN_CLASS_P (r))
              /* Set up DECL_INITIAL, since tsubst doesn't.  */
              DECL_INITIAL (r) = tsubst_expr (DECL_INITIAL (t), args,
                                              /*complain=*/1, NULL_TREE);
            start_decl_1 (r);
            DECL_IN_AGGR_P (r) = 1;
            DECL_EXTERNAL (r) = 1;
            cp_finish_decl (r, DECL_INITIAL (r), NULL_TREE, 0, 0);
            if (DECL_DEFINED_IN_CLASS_P (r))
              check_static_variable_definition (r, TREE_TYPE (r));
          }
        
        /* R will have a TREE_CHAIN if and only if it has already been
           processed by finish_member_declaration.  This can happen
           if, for example, it is a TYPE_DECL for a class-scoped
           ENUMERAL_TYPE; such a thing will already have been added to
           the field list by tsubst_enum above.  */
        if (!TREE_CHAIN (r))
          {
            set_current_access_from_decl (r);
            finish_member_declaration (r);
          }
      }

  /* Set up the list (TYPE_METHODS) and vector (CLASSTYPE_METHOD_VEC)
     for this instantiation.  */
  for (t = TYPE_METHODS (pattern); t; t = TREE_CHAIN (t))
    {
      tree r = tsubst (t, args, /*complain=*/1, NULL_TREE);
      set_current_access_from_decl (r);
      finish_member_declaration (r);
    }

  /* Construct the DECL_FRIENDLIST for the new class type.  */
  typedecl = TYPE_MAIN_DECL (type);
  for (t = DECL_FRIENDLIST (TYPE_MAIN_DECL (pattern));
       t != NULL_TREE;
       t = TREE_CHAIN (t))
    {
      tree friends;

      DECL_FRIENDLIST (typedecl)
        = tree_cons (TREE_PURPOSE (t), NULL_TREE, 
                     DECL_FRIENDLIST (typedecl));

      for (friends = TREE_VALUE (t);
           friends != NULL_TREE;
           friends = TREE_CHAIN (friends))
        {
          if (TREE_PURPOSE (friends) == error_mark_node)
            {
              TREE_VALUE (DECL_FRIENDLIST (typedecl))
                = tree_cons (error_mark_node, 
                             tsubst_friend_function (TREE_VALUE (friends),
                                                     args),
                             TREE_VALUE (DECL_FRIENDLIST (typedecl)));
            }
          else
            {
              TREE_VALUE (DECL_FRIENDLIST (typedecl))
                = tree_cons (tsubst (TREE_PURPOSE (friends), args, 
                                     /*complain=*/1, NULL_TREE),
                             NULL_TREE,
                             TREE_VALUE (DECL_FRIENDLIST (typedecl)));

            }
        }
    }

  for (t = CLASSTYPE_FRIEND_CLASSES (pattern);
       t != NULL_TREE;
       t = TREE_CHAIN (t))
    {
      tree friend_type = TREE_VALUE (t);
      tree new_friend_type;

      if (TREE_CODE (friend_type) == TEMPLATE_DECL)
        new_friend_type = tsubst_friend_class (friend_type, args);
      else if (uses_template_parms (friend_type))
        new_friend_type = tsubst (friend_type, args, /*complain=*/1,
                                  NULL_TREE);
      else 
        /* The call to xref_tag_from_type does injection for friend
           classes.  */
        new_friend_type = 
          xref_tag_from_type (friend_type, NULL_TREE, 1);


      if (TREE_CODE (friend_type) == TEMPLATE_DECL)
        /* Trick make_friend_class into realizing that the friend
           we're adding is a template, not an ordinary class.  It's
           important that we use make_friend_class since it will
           perform some error-checking and output cross-reference
           information.  */
        ++processing_template_decl;

      make_friend_class (type, new_friend_type);

      if (TREE_CODE (friend_type) == TEMPLATE_DECL)
        --processing_template_decl;
    }

  /* This does injection for friend functions. */
  if (!processing_template_decl)
    {
      t = tsubst (DECL_TEMPLATE_INJECT (template), args,
                  /*complain=*/1, NULL_TREE);

      for (; t; t = TREE_CHAIN (t))
        {
          tree d = TREE_VALUE (t);

          if (TREE_CODE (d) == TYPE_DECL)
            /* Already injected.  */;
          else
            pushdecl (d);
        }
    } 

  for (t = TYPE_FIELDS (type); t; t = TREE_CHAIN (t))
    if (TREE_CODE (t) == FIELD_DECL)
      {
        TREE_TYPE (t) = complete_type (TREE_TYPE (t));
        require_complete_type (t);
      }

  /* Set the file and line number information to whatever is given for
     the class itself.  This puts error messages involving generated
     implicit functions at a predictable point, and the same point
     that would be used for non-template classes.  */
  lineno = DECL_SOURCE_LINE (typedecl);
  input_filename = DECL_SOURCE_FILE (typedecl);

  unreverse_member_declarations (type);
  type = finish_struct_1 (type, 0);
  CLASSTYPE_GOT_SEMICOLON (type) = 1;

  /* Clear this now so repo_template_used is happy.  */
  TYPE_BEING_DEFINED (type) = 0;
  repo_template_used (type);

  popclass (0);
  pop_from_top_level ();
  pop_tinst_level ();

 end:
  pop_momentary ();

  return type;
}

static int
list_eq (t1, t2)
     tree t1, t2;
{
  if (t1 == NULL_TREE)
    return t2 == NULL_TREE;
  if (t2 == NULL_TREE)
    return 0;
  /* Don't care if one declares its arg const and the other doesn't -- the
     main variant of the arg type is all that matters.  */
  if (TYPE_MAIN_VARIANT (TREE_VALUE (t1))
      != TYPE_MAIN_VARIANT (TREE_VALUE (t2)))
    return 0;
  return list_eq (TREE_CHAIN (t1), TREE_CHAIN (t2));
}

/* If arg is a non-type template parameter that does not depend on template
   arguments, fold it like we weren't in the body of a template.  */

static tree
maybe_fold_nontype_arg (arg)
     tree arg;
{
  if (TREE_CODE_CLASS (TREE_CODE (arg)) != 't'
      && !uses_template_parms (arg))
    {
      /* Sometimes, one of the args was an expression involving a
         template constant parameter, like N - 1.  Now that we've
         tsubst'd, we might have something like 2 - 1.  This will
         confuse lookup_template_class, so we do constant folding
         here.  We have to unset processing_template_decl, to
         fool build_expr_from_tree() into building an actual
         tree.  */

      int saved_processing_template_decl = processing_template_decl; 
      processing_template_decl = 0;
      arg = fold (build_expr_from_tree (arg));
      processing_template_decl = saved_processing_template_decl; 
    }
  return arg;
}

/* Return the TREE_VEC with the arguments for the innermost template header,
   where ARGS is either that or the VEC of VECs for all the
   arguments.  */

tree
innermost_args (args)
     tree args;
{
  return TMPL_ARGS_LEVEL (args, TMPL_ARGS_DEPTH (args));
}

/* Substitute ARGS into the vector of template arguments T.  */

static tree
tsubst_template_arg_vector (t, args, complain)
     tree t;
     tree args;
     int complain;
{
  int len = TREE_VEC_LENGTH (t), need_new = 0, i;
  tree *elts = (tree *) alloca (len * sizeof (tree));
  
  bzero ((char *) elts, len * sizeof (tree));
  
  for (i = 0; i < len; i++)
    {
      if (TREE_VEC_ELT (t, i) != NULL_TREE
          && TREE_CODE (TREE_VEC_ELT (t, i)) == TREE_VEC)
        elts[i] = tsubst_template_arg_vector (TREE_VEC_ELT (t, i),
                                              args, complain);
      else
        elts[i] = maybe_fold_nontype_arg
          (tsubst_expr (TREE_VEC_ELT (t, i), args, complain,
                        NULL_TREE));
      
      if (elts[i] != TREE_VEC_ELT (t, i))
        need_new = 1;
    }
  
  if (!need_new)
    return t;
  
  t = make_temp_vec (len);
  for (i = 0; i < len; i++)
    TREE_VEC_ELT (t, i) = elts[i];
  
  return t;
}

/* Return the result of substituting ARGS into the template parameters
   given by PARMS.  If there are m levels of ARGS and m + n levels of
   PARMS, then the result will contain n levels of PARMS.  For
   example, if PARMS is `template <class T> template <class U>
   template <T*, U, class V>' and ARGS is {{int}, {double}} then the
   result will be `template <int*, double, class V>'.  */

static tree
tsubst_template_parms (parms, args, complain)
     tree parms;
     tree args;
     int complain;
{
  tree r;
  tree* new_parms = &r;

  for (new_parms = &r;
       TMPL_PARMS_DEPTH (parms) > TMPL_ARGS_DEPTH (args);
       new_parms = &(TREE_CHAIN (*new_parms)),
         parms = TREE_CHAIN (parms))
    {
      tree new_vec = 
        make_tree_vec (TREE_VEC_LENGTH (TREE_VALUE (parms)));
      int i;
      
      for (i = 0; i < TREE_VEC_LENGTH (new_vec); ++i)
        {
          tree default_value =
            TREE_PURPOSE (TREE_VEC_ELT (TREE_VALUE (parms), i));
          tree parm_decl = 
            TREE_VALUE (TREE_VEC_ELT (TREE_VALUE (parms), i));
          
          TREE_VEC_ELT (new_vec, i)
            = build_tree_list (tsubst (default_value, args, complain,
                                       NULL_TREE), 
                               tsubst (parm_decl, args, complain,
                                       NULL_TREE));
        }
      
      *new_parms = 
        tree_cons (build_int_2 (0, (TMPL_PARMS_DEPTH (parms) 
                                    - TMPL_ARGS_DEPTH (args))),
                   new_vec, NULL_TREE);
    }

  return r;
}

/* Substitute the ARGS into the indicated aggregate (or enumeration)
   type T.  If T is not an aggregate or enumeration type, it is
   handled as if by tsubst.  IN_DECL is as for tsubst.  If
   ENTERING_SCOPE is non-zero, T is the context for a template which
   we are presently tsubst'ing.  Return the subsituted value.  */

static tree
tsubst_aggr_type (t, args, complain, in_decl, entering_scope)
     tree t;
     tree args;
     int complain;
     tree in_decl;
     int entering_scope;
{
  if (t == NULL_TREE)
    return NULL_TREE;

  switch (TREE_CODE (t))
    {
    case RECORD_TYPE:
      if (TYPE_PTRMEMFUNC_P (t))
        {
          tree r = build_ptrmemfunc_type
            (tsubst (TYPE_PTRMEMFUNC_FN_TYPE (t), args, complain, in_decl));
          return cp_build_qualified_type (r, TYPE_QUALS (t));
        }

      /* else fall through */
    case ENUMERAL_TYPE:
    case UNION_TYPE:
      if (TYPE_TEMPLATE_INFO (t))
        {
          tree argvec;
          tree context;
          tree r;

          /* First, determine the context for the type we are looking
             up.  */
          if (TYPE_CONTEXT (t) != NULL_TREE)
            context = tsubst_aggr_type (TYPE_CONTEXT (t), args,
                                        complain,
                                        in_decl, /*entering_scope=*/1);
          else
            context = NULL_TREE;

          /* Then, figure out what arguments are appropriate for the
             type we are trying to find.  For example, given:

               template <class T> struct S;
               template <class T, class U> void f(T, U) { S<U> su; }

             and supposing that we are instantiating f<int, double>,
             then our ARGS will be {int, double}, but, when looking up
             S we only want {double}.  */
          push_momentary ();
          argvec = tsubst_template_arg_vector (TYPE_TI_ARGS (t), args,
                                               complain);

          r = lookup_template_class (t, argvec, in_decl, context,
                                     entering_scope);
          pop_momentary ();

          return cp_build_qualified_type (r, TYPE_QUALS (t));
        }
      else 
        /* This is not a template type, so there's nothing to do.  */
        return t;

    default:
      return tsubst (t, args, complain, in_decl);
    }
}

/* Substitute the ARGS into the T, which is a _DECL.  TYPE is the
   (already computed) substitution of ARGS into TREE_TYPE (T), if
   appropriate.  Return the result of the substitution.  IN_DECL is as
   for tsubst.  */

static tree
tsubst_decl (t, args, type, in_decl)
     tree t;
     tree args;
     tree type;
     tree in_decl;
{
  int saved_lineno;
  char* saved_filename;
  tree r = NULL_TREE;

  /* Set the filename and linenumber to improve error-reporting.  */
  saved_lineno = lineno;
  saved_filename = input_filename;
  lineno = DECL_SOURCE_LINE (t);
  input_filename = DECL_SOURCE_FILE (t);

  switch (TREE_CODE (t))
    {
    case TEMPLATE_DECL:
      {
        /* We can get here when processing a member template function
           of a template class.  */
        tree decl = DECL_TEMPLATE_RESULT (t);
        tree spec;
        int is_template_template_parm = DECL_TEMPLATE_TEMPLATE_PARM_P (t);

        if (!is_template_template_parm)
          {
            /* We might already have an instance of this template.
               The ARGS are for the surrounding class type, so the
               full args contain the tsubst'd args for the context,
               plus the innermost args from the template decl.  */
            tree tmpl_args = DECL_CLASS_TEMPLATE_P (t) 
              ? CLASSTYPE_TI_ARGS (TREE_TYPE (t))
              : DECL_TI_ARGS (DECL_RESULT (t));
            tree full_args;
            
            push_momentary ();
            full_args = tsubst_template_arg_vector (tmpl_args, args,
                                                    /*complain=*/1);

            /* tsubst_template_arg_vector doesn't copy the vector if
               nothing changed.  But, *something* should have
               changed.  */
            my_friendly_assert (full_args != tmpl_args, 0);

            spec = retrieve_specialization (t, full_args);
            pop_momentary ();
            if (spec != NULL_TREE)
              {
                r = spec;
                break;
              }
          }

        /* Make a new template decl.  It will be similar to the
           original, but will record the current template arguments. 
           We also create a new function declaration, which is just
           like the old one, but points to this new template, rather
           than the old one.  */
        r = copy_node (t);
        copy_lang_decl (r);
        my_friendly_assert (DECL_LANG_SPECIFIC (r) != 0, 0);
        TREE_CHAIN (r) = NULL_TREE;

        if (is_template_template_parm)
          {
            tree new_decl = tsubst (decl, args, /*complain=*/1, in_decl);
            DECL_RESULT (r) = new_decl;
            TREE_TYPE (r) = TREE_TYPE (new_decl);
            break;
          }

        DECL_CONTEXT (r) 
          = tsubst_aggr_type (DECL_CONTEXT (t), args, /*complain=*/1,
                              in_decl, /*entering_scope=*/1);
        DECL_CLASS_CONTEXT (r) 
          = tsubst_aggr_type (DECL_CLASS_CONTEXT (t), args, 
                              /*complain=*/1, in_decl, 
                              /*entering_scope=*/1); 
        DECL_TEMPLATE_INFO (r) = build_tree_list (t, args);

        if (TREE_CODE (decl) == TYPE_DECL)
          {
            tree new_type = tsubst (TREE_TYPE (t), args,
                                    /*complain=*/1, in_decl);
            TREE_TYPE (r) = new_type;
            CLASSTYPE_TI_TEMPLATE (new_type) = r;
            DECL_RESULT (r) = TYPE_MAIN_DECL (new_type);
            DECL_TI_ARGS (r) = CLASSTYPE_TI_ARGS (new_type);
          }
        else
          {
            tree new_decl = tsubst (decl, args, /*complain=*/1, in_decl);
            DECL_RESULT (r) = new_decl;
            DECL_TI_TEMPLATE (new_decl) = r;
            TREE_TYPE (r) = TREE_TYPE (new_decl);
            DECL_TI_ARGS (r) = DECL_TI_ARGS (new_decl);
          }

        SET_DECL_IMPLICIT_INSTANTIATION (r);
        DECL_TEMPLATE_INSTANTIATIONS (r) = NULL_TREE;
        DECL_TEMPLATE_SPECIALIZATIONS (r) = NULL_TREE;

        /* The template parameters for this new template are all the
           template parameters for the old template, except the
           outermost level of parameters. */
        DECL_TEMPLATE_PARMS (r) 
          = tsubst_template_parms (DECL_TEMPLATE_PARMS (t), args,
                                   /*complain=*/1);

        if (PRIMARY_TEMPLATE_P (t))
          DECL_PRIMARY_TEMPLATE (r) = r;

        /* We don't partially instantiate partial specializations.  */
        if (TREE_CODE (decl) == TYPE_DECL)
          break;

        for (spec = DECL_TEMPLATE_SPECIALIZATIONS (t);
             spec != NULL_TREE;
             spec = TREE_CHAIN (spec))
          {
            /* It helps to consider example here.  Consider:

               template <class T>
               struct S {
                 template <class U>
                 void f(U u);

                 template <>
                 void f(T* t) {}
               };
               
               Now, for example, we are instantiating S<int>::f(U u).  
               We want to make a template:

               template <class U>
               void S<int>::f(U);

               It will have a specialization, for the case U = int*, of
               the form:

               template <>
               void S<int>::f<int*>(int*);

               This specialization will be an instantiation of
               the specialization given in the declaration of S, with
               argument list int*.  */

            tree fn = TREE_VALUE (spec);
            tree spec_args;
            tree new_fn;

            if (!DECL_TEMPLATE_SPECIALIZATION (fn))
              /* Instantiations are on the same list, but they're of
                 no concern to us.  */
              continue;

            if (TREE_CODE (fn) != TEMPLATE_DECL)
              /* A full specialization.  There's no need to record
                 that here.  */
              continue;

            spec_args = tsubst (DECL_TI_ARGS (fn), args,
                                /*complain=*/1, in_decl); 
            new_fn = tsubst (DECL_RESULT (most_general_template (fn)), 
                             spec_args, /*complain=*/1, in_decl); 
            DECL_TI_TEMPLATE (new_fn) = fn;
            register_specialization (new_fn, r, 
                                     innermost_args (spec_args));
          }

        /* Record this partial instantiation.  */
        register_specialization (r, t, 
                                 DECL_TI_ARGS (DECL_RESULT (r)));

      }
      break;

    case FUNCTION_DECL:
      {
        tree ctx;
        tree argvec = NULL_TREE;
        tree gen_tmpl;
        int member;
        int args_depth;
        int parms_depth;

        /* Nobody should be tsubst'ing into non-template functions.  */
        my_friendly_assert (DECL_TEMPLATE_INFO (t) != NULL_TREE, 0);

        if (TREE_CODE (DECL_TI_TEMPLATE (t)) == TEMPLATE_DECL)
          {
            tree spec;

            /* Allocate template arguments on the momentary obstack,
               in case we don't need to keep them.  */
            push_momentary ();

            /* Calculate the most general template of which R is a
               specialization, and the complete set of arguments used to
               specialize R.  */
            gen_tmpl = most_general_template (DECL_TI_TEMPLATE (t));
            argvec 
              = tsubst_template_arg_vector (DECL_TI_ARGS 
                                            (DECL_TEMPLATE_RESULT (gen_tmpl)),
                                            args, /*complain=*/1); 

            /* Check to see if we already have this specialization.  */
            spec = retrieve_specialization (gen_tmpl, argvec);

            if (spec)
              {
                r = spec;
                pop_momentary ();
                break;
              }

            /* We're going to need to keep the ARGVEC, so we copy it
               here.  */
            argvec = copy_to_permanent (argvec);
            pop_momentary ();

            /* Here, we deal with the peculiar case:

                 template <class T> struct S { 
                   template <class U> friend void f();
                 };
                 template <class U> friend void f() {}
                 template S<int>;
                 template void f<double>();

               Here, the ARGS for the instantiation of will be {int,
               double}.  But, we only need as many ARGS as there are
               levels of template parameters in CODE_PATTERN.  We are
               careful not to get fooled into reducing the ARGS in
               situations like:

                 template <class T> struct S { template <class U> void f(U); }
                 template <class T> template <> void S<T>::f(int) {}

               which we can spot because the pattern will be a
               specialization in this case.  */
            args_depth = TMPL_ARGS_DEPTH (args);
            parms_depth = 
              TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (DECL_TI_TEMPLATE (t))); 
            if (args_depth > parms_depth
                && !DECL_TEMPLATE_SPECIALIZATION (t))
              {
                my_friendly_assert (DECL_FRIEND_P (t), 0);

                if (parms_depth > 1)
                  {
                    int i;

                    args = make_temp_vec (parms_depth);
                    for (i = 0; i < parms_depth; ++i)
                      TREE_VEC_ELT (args, i) = 
                        TREE_VEC_ELT (args, i + (args_depth - parms_depth));
                  }
                else
                  args = TREE_VEC_ELT (args, args_depth - parms_depth);
              }
          }
        else
          {
            /* This special case arises when we have something like this:

                 template <class T> struct S { 
                   friend void f<int>(int, double); 
                 };

               Here, the DECL_TI_TEMPLATE for the friend declaration
               will be a LOOKUP_EXPR or an IDENTIFIER_NODE.  We are
               being called from tsubst_friend_function, and we want
               only to create a new decl (R) with appropriate types so
               that we can call determine_specialization.  */
            my_friendly_assert ((TREE_CODE (DECL_TI_TEMPLATE (t)) 
                                 == LOOKUP_EXPR)
                                || (TREE_CODE (DECL_TI_TEMPLATE (t))
                                    == IDENTIFIER_NODE), 0);
            gen_tmpl = NULL_TREE;
          }

        if (DECL_CLASS_SCOPE_P (t))
          {
            if (DECL_NAME (t) == constructor_name (DECL_CONTEXT (t)))
              member = 2;
            else
              member = 1;
            ctx = tsubst_aggr_type (DECL_CLASS_CONTEXT (t), args, 
                                    /*complain=*/1, t, 
                                    /*entering_scope=*/1);
          }
        else
          {
            member = 0;
            ctx = NULL_TREE;
          }
        type = tsubst (type, args, /*complain=*/1, in_decl);

        /* We do NOT check for matching decls pushed separately at this
           point, as they may not represent instantiations of this
           template, and in any case are considered separate under the
           discrete model.  Instead, see add_maybe_template.  */

        r = copy_node (t);
        copy_lang_decl (r);
        DECL_USE_TEMPLATE (r) = 0;
        TREE_TYPE (r) = type;

        DECL_CONTEXT (r)
          = tsubst_aggr_type (DECL_CONTEXT (t), args, /*complain=*/1, t,
                              /*entering_scope=*/1);
        DECL_CLASS_CONTEXT (r) = ctx;

        if (member && IDENTIFIER_TYPENAME_P (DECL_NAME (r)))
          /* Type-conversion operator.  Reconstruct the name, in
             case it's the name of one of the template's parameters.  */
          DECL_NAME (r) = build_typename_overload (TREE_TYPE (type));

        DECL_ARGUMENTS (r) = tsubst (DECL_ARGUMENTS (t), args,
                                     /*complain=*/1, t);
        DECL_MAIN_VARIANT (r) = r;
        DECL_RESULT (r) = NULL_TREE;

        TREE_STATIC (r) = 0;
        TREE_PUBLIC (r) = TREE_PUBLIC (t);
        DECL_EXTERNAL (r) = 1;
        DECL_INTERFACE_KNOWN (r) = 0;
        DECL_DEFER_OUTPUT (r) = 0;
        TREE_CHAIN (r) = NULL_TREE;
        DECL_PENDING_INLINE_INFO (r) = 0;
        TREE_USED (r) = 0;

        /* Set up the DECL_TEMPLATE_INFO for R and compute its mangled
           name.  There's no need to do this in the special friend
           case mentioned above where GEN_TMPL is NULL.  */
        if (gen_tmpl)
          {
            /* The ARGVEC was built on the momentary obstack.  Make it
               permanent now.  */
            argvec = copy_to_permanent (argvec);
            DECL_TEMPLATE_INFO (r) 
              = perm_tree_cons (gen_tmpl, argvec, NULL_TREE);
            SET_DECL_IMPLICIT_INSTANTIATION (r);
            register_specialization (r, gen_tmpl, argvec);

            /* Set the mangled name for R.  */
            if (DECL_DESTRUCTOR_P (t))
              DECL_ASSEMBLER_NAME (r) = build_destructor_name (ctx);
            else 
              {
                /* Instantiations of template functions must be mangled
                   specially, in order to conform to 14.5.5.1
                   [temp.over.link].  */
                tree tmpl = DECL_TI_TEMPLATE (t);
                
                /* TMPL will be NULL if this is a specialization of a
                   member function of a template class.  */
                if (name_mangling_version < 1
                    || tmpl == NULL_TREE
                    || (member && !is_member_template (tmpl)
                        && !DECL_TEMPLATE_INFO (tmpl)))
                  set_mangled_name_for_decl (r);
                else
                  set_mangled_name_for_template_decl (r);
              }
            
            DECL_RTL (r) = 0;
            make_decl_rtl (r, NULL_PTR, 1);
            
            /* Like grokfndecl.  If we don't do this, pushdecl will
               mess up our TREE_CHAIN because it doesn't find a
               previous decl.  Sigh.  */
            if (member
                && ! uses_template_parms (r)
                && (IDENTIFIER_GLOBAL_VALUE (DECL_ASSEMBLER_NAME (r)) 
                    == NULL_TREE))
              SET_IDENTIFIER_GLOBAL_VALUE (DECL_ASSEMBLER_NAME (r), r);
          }

        if (DECL_CONSTRUCTOR_P (r))
          {
            maybe_retrofit_in_chrg (r);
            grok_ctor_properties (ctx, r);
          }
        if (IDENTIFIER_OPNAME_P (DECL_NAME (r)))
          grok_op_properties (r, DECL_VIRTUAL_P (r), DECL_FRIEND_P (r));
      }
      break;

    case PARM_DECL:
      {
        r = copy_node (t);
        TREE_TYPE (r) = type;
        if (TREE_CODE (DECL_INITIAL (r)) != TEMPLATE_PARM_INDEX)
          DECL_INITIAL (r) = TREE_TYPE (r);
        else
          DECL_INITIAL (r) = tsubst (DECL_INITIAL (r), args,
                                     /*complain=*/1, in_decl);

        DECL_CONTEXT (r) = NULL_TREE;
#ifdef PROMOTE_PROTOTYPES
        if ((TREE_CODE (type) == INTEGER_TYPE
             || TREE_CODE (type) == ENUMERAL_TYPE)
            && TYPE_PRECISION (type) < TYPE_PRECISION (integer_type_node))
          DECL_ARG_TYPE (r) = integer_type_node;
#endif
        if (TREE_CHAIN (t))
          TREE_CHAIN (r) = tsubst (TREE_CHAIN (t), args,
                                   /*complain=*/1, TREE_CHAIN (t));
      }
      break;

    case FIELD_DECL:
      {
        r = copy_node (t);
        TREE_TYPE (r) = type;
        copy_lang_decl (r);
#if 0
        DECL_FIELD_CONTEXT (r) = tsubst (DECL_FIELD_CONTEXT (t), args, 
                                         /*complain=*/1, in_decl);
#endif
        DECL_INITIAL (r) = tsubst_expr (DECL_INITIAL (t), args,
                                        /*complain=*/1, in_decl);
        TREE_CHAIN (r) = NULL_TREE;
        if (TREE_CODE (type) == VOID_TYPE) 
          cp_error_at ("instantiation of `%D' as type void", r);
      }
      break;

    case USING_DECL:
      {
        r = copy_node (t);
        DECL_INITIAL (r)
          = tsubst_copy (DECL_INITIAL (t), args, /*complain=*/1, in_decl);
        TREE_CHAIN (r) = NULL_TREE;
      }
      break;

    case VAR_DECL:
      {
        tree argvec;
        tree gen_tmpl;
        tree spec;
        tree tmpl;
        tree ctx = tsubst_aggr_type (DECL_CONTEXT (t), args, 
                                     /*complain=*/1,
                                     in_decl, /*entering_scope=*/1);
        
        /* Nobody should be tsubst'ing into non-template variables.  */
        my_friendly_assert (DECL_LANG_SPECIFIC (t) 
                            && DECL_TEMPLATE_INFO (t) != NULL_TREE, 0);

        /* Check to see if we already have this specialization.  */
        tmpl = DECL_TI_TEMPLATE (t);
        gen_tmpl = most_general_template (tmpl);
        argvec = tsubst (DECL_TI_ARGS (t), args, /*complain=*/1, in_decl);
        spec = retrieve_specialization (gen_tmpl, argvec);
        
        if (spec)
          {
            r = spec;
            break;
          }

        r = copy_node (t);
        TREE_TYPE (r) = type;
        DECL_CONTEXT (r) = ctx;
        if (TREE_STATIC (r))
          DECL_ASSEMBLER_NAME (r)
            = build_static_name (DECL_CONTEXT (r), DECL_NAME (r));

        /* Don't try to expand the initializer until someone tries to use
           this variable; otherwise we run into circular dependencies.  */
        DECL_INITIAL (r) = NULL_TREE;
        DECL_RTL (r) = 0;
        DECL_SIZE (r) = 0;
        copy_lang_decl (r);
        DECL_CLASS_CONTEXT (r) = DECL_CONTEXT (r);

        DECL_TEMPLATE_INFO (r) = perm_tree_cons (tmpl, argvec, NULL_TREE);
        SET_DECL_IMPLICIT_INSTANTIATION (r);
        register_specialization (r, gen_tmpl, argvec);

        TREE_CHAIN (r) = NULL_TREE;
        if (TREE_CODE (type) == VOID_TYPE)
          cp_error_at ("instantiation of `%D' as type void", r);
      }
      break;

    case TYPE_DECL:
      if (t == TYPE_NAME (TREE_TYPE (t)))
        r = TYPE_NAME (type);
      else
        {
          r = copy_node (t);
          TREE_TYPE (r) = type;
          DECL_CONTEXT (r) = current_class_type;
          TREE_CHAIN (r) = NULL_TREE;
        }
      break;

    default:
      my_friendly_abort (0);
    } 

  /* Restore the file and line information.  */
  lineno = saved_lineno;
  input_filename = saved_filename;

  return r;
}

/* Substitue into the ARG_TYPES of a function type.  */

static tree
tsubst_arg_types (arg_types, args, complain, in_decl)
     tree arg_types;
     tree args;
     int complain;
     tree in_decl;
{
  tree remaining_arg_types;
  tree type;

  if (!arg_types || arg_types == void_list_node)
    return arg_types;
  
  remaining_arg_types = tsubst_arg_types (TREE_CHAIN (arg_types),
                                          args, complain, in_decl);
  if (remaining_arg_types == error_mark_node)
    return error_mark_node;

  type = tsubst (TREE_VALUE (arg_types), args, complain, in_decl);
  if (type == error_mark_node)
    return error_mark_node;

  /* Do array-to-pointer, function-to-pointer conversion, and ignore
     top-level qualifiers as required.  */
  type = TYPE_MAIN_VARIANT (type_decays_to (type));

  /* Note that we do not substitute into default arguments here.  The
     standard mandates that they be instantiated only when needed,
     which is done in build_over_call.  */
  return hash_tree_cons_simple (TREE_PURPOSE (arg_types), type,
                                remaining_arg_types);
                         
}

/* Substitute into a FUNCTION_TYPE or METHOD_TYPE.  This routine does
   *not* handle the exception-specification for FNTYPE, because the
   initial substitution of explicitly provided template parameters
   during argument deduction forbids substitution into the
   exception-specification:

     [temp.deduct]

     All references in the function type of the function template to  the
     corresponding template parameters are replaced by the specified tem-
     plate argument values.  If a substitution in a template parameter or
     in  the function type of the function template results in an invalid
     type, type deduction fails.  [Note: The equivalent  substitution  in
     exception specifications is done only when the function is instanti-
     ated, at which point a program is  ill-formed  if  the  substitution
     results in an invalid type.]  */

static tree
tsubst_function_type (t, args, complain, in_decl)
     tree t;
     tree args;
     int complain;
     tree in_decl;
{
  tree return_type;
  tree arg_types;
  tree fntype;

  /* The TYPE_CONTEXT is not used for function/method types.  */
  my_friendly_assert (TYPE_CONTEXT (t) == NULL_TREE, 0);

  /* Substitue the return type.  */
  return_type = tsubst (TREE_TYPE (t), args, complain, in_decl);
  if (return_type == error_mark_node)
    return error_mark_node;

  /* Substitue the argument types.  */
  arg_types = tsubst_arg_types (TYPE_ARG_TYPES (t), args,
                                complain, in_decl); 
  if (arg_types == error_mark_node)
    return error_mark_node;
  
  /* Construct a new type node and return it.  */
  if (TREE_CODE (t) == FUNCTION_TYPE)
    fntype = build_function_type (return_type, arg_types);
  else
    {
      tree r = TREE_TYPE (TREE_VALUE (arg_types));
      if (! IS_AGGR_TYPE (r))
        {
          /* [temp.deduct]
             
             Type deduction may fail for any of the following
             reasons:
             
             -- Attempting to create "pointer to member of T" when T
             is not a class type.  */
          if (complain)
            cp_error ("creating pointer to member function of non-class type `%T'",
                      r);
          return error_mark_node;
        }
      
      fntype = build_cplus_method_type (r, return_type, TREE_CHAIN
                                        (arg_types));
    }
  fntype = build_qualified_type (fntype, TYPE_QUALS (t));
  
  return fntype;  
}

/* Substitute into the PARMS of a call-declarator.  */

static tree
tsubst_call_declarator_parms (parms, args, complain, in_decl)
     tree parms;
     tree args;
     int complain;
     tree in_decl;
{
  tree new_parms;
  tree type;
  tree defarg;

  if (!parms || parms == void_list_node)
    return parms;
  
  new_parms = tsubst_call_declarator_parms (TREE_CHAIN (parms),
                                            args, complain, in_decl);

  /* Figure out the type of this parameter.  */
  type = tsubst (TREE_VALUE (parms), args, complain, in_decl);
  
  /* Figure out the default argument as well.  Note that we use
     tsubst_expr since the default argument is really an expression.  */
  defarg = tsubst_expr (TREE_PURPOSE (parms), args, complain, in_decl);

  /* Chain this parameter on to the front of those we have already
     processed.  We don't use hash_tree_cons because that function
     doesn't check TREE_PARMLIST.  */
  new_parms = tree_cons (defarg, type, new_parms);

  /* And note that these are parameters.  */
  TREE_PARMLIST (new_parms) = 1;
  
  return new_parms;
}

/* Take the tree structure T and replace template parameters used
   therein with the argument vector ARGS.  IN_DECL is an associated
   decl for diagnostics.  If an error occurs, returns ERROR_MARK_NODE.
   An appropriate error message is issued only if COMPLAIN is
   non-zero.  Note that we must be relatively non-tolerant of
   extensions here, in order to preserve conformance; if we allow
   substitutions that should not be allowed, we may allow argument
   deductions that should not succeed, and therefore report ambiguous
   overload situations where there are none.  In theory, we could
   allow the substitution, but indicate that it should have failed,
   and allow our caller to make sure that the right thing happens, but
   we don't try to do this yet.

   This function is used for dealing with types, decls and the like;
   for expressions, use tsubst_expr or tsubst_copy.  */

tree
tsubst (t, args, complain, in_decl)
     tree t, args;
     int complain;
     tree in_decl;
{
  tree type, r;

  if (t == NULL_TREE || t == error_mark_node
      || t == integer_type_node
      || t == void_type_node
      || t == char_type_node
      || TREE_CODE (t) == NAMESPACE_DECL)
    return t;

  if (TREE_CODE (t) == IDENTIFIER_NODE)
    type = IDENTIFIER_TYPE_VALUE (t);
  else
    type = TREE_TYPE (t);
  if (type == unknown_type_node)
    my_friendly_abort (42);

  if (type && TREE_CODE (t) != FUNCTION_DECL
      && TREE_CODE (t) != TYPENAME_TYPE
      && TREE_CODE (t) != TEMPLATE_DECL
      && TREE_CODE (t) != IDENTIFIER_NODE
      && TREE_CODE (t) != FUNCTION_TYPE
      && TREE_CODE (t) != METHOD_TYPE)
    type = tsubst (type, args, complain, in_decl);
  if (type == error_mark_node)
    return error_mark_node;

  if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
    return tsubst_decl (t, args, type, in_decl);

  switch (TREE_CODE (t))
    {
    case RECORD_TYPE:
    case UNION_TYPE:
    case ENUMERAL_TYPE:
      return tsubst_aggr_type (t, args, complain, in_decl,
                               /*entering_scope=*/0);

    case ERROR_MARK:
    case IDENTIFIER_NODE:
    case OP_IDENTIFIER:
    case VOID_TYPE:
    case REAL_TYPE:
    case COMPLEX_TYPE:
    case BOOLEAN_TYPE:
    case INTEGER_CST:
    case REAL_CST:
    case STRING_CST:
      return t;

    case INTEGER_TYPE:
      if (t == integer_type_node)
        return t;

      if (TREE_CODE (TYPE_MIN_VALUE (t)) == INTEGER_CST
          && TREE_CODE (TYPE_MAX_VALUE (t)) == INTEGER_CST)
        return t;

      {
        tree max, omax = TREE_OPERAND (TYPE_MAX_VALUE (t), 0);

        max = tsubst_expr (omax, args, complain, in_decl);
        if (max == error_mark_node)
          return error_mark_node;

        if (processing_template_decl)
          {
            tree itype = make_node (INTEGER_TYPE);
            TYPE_MIN_VALUE (itype) = size_zero_node;
            TYPE_MAX_VALUE (itype) = build_min (MINUS_EXPR, sizetype, max,
                                                integer_one_node);
            return itype;
          }

        if (integer_zerop (omax))
          {
            /* Still allow an explicit array of size zero.  */
            if (pedantic)
              pedwarn ("creating array with size zero");
          }
        else if (integer_zerop (max) || INT_CST_LT (max, integer_zero_node))
          {
            /* [temp.deduct]

               Type deduction may fail for any of the following
               reasons:  

                 Attempting to create an array with a size that is
                 zero or negative.  */
            if (complain)
              cp_error ("creating array with size `%E'", max);

            return error_mark_node;
          }

        max = fold (build_binary_op (MINUS_EXPR, max, integer_one_node, 1));
        if (!TREE_PERMANENT (max) && !allocation_temporary_p ())
          max = copy_to_permanent (max);
        return build_index_type (max);
      }

    case TEMPLATE_TYPE_PARM:
    case TEMPLATE_TEMPLATE_PARM:
    case TEMPLATE_PARM_INDEX:
      {
        int idx;
        int level;
        int levels;

        r = NULL_TREE;

        if (TREE_CODE (t) == TEMPLATE_TYPE_PARM
            || TREE_CODE (t) == TEMPLATE_TEMPLATE_PARM)
          {
            idx = TEMPLATE_TYPE_IDX (t);
            level = TEMPLATE_TYPE_LEVEL (t);
          }
        else
          {
            idx = TEMPLATE_PARM_IDX (t);
            level = TEMPLATE_PARM_LEVEL (t);
          }

        if (TREE_VEC_LENGTH (args) > 0)
          {
            tree arg = NULL_TREE;

            levels = TMPL_ARGS_DEPTH (args);
            if (level <= levels)
              arg = TMPL_ARG (args, level, idx);

            if (arg == error_mark_node)
              return error_mark_node;
            else if (arg != NULL_TREE)
              {
                if (TREE_CODE (t) == TEMPLATE_TYPE_PARM)
                  {
                    my_friendly_assert (TREE_CODE_CLASS (TREE_CODE (arg))
                                        == 't', 0);
                    return cp_build_qualified_type
                      (arg, CP_TYPE_QUALS (arg) | CP_TYPE_QUALS (t));
                  }
                else if (TREE_CODE (t) == TEMPLATE_TEMPLATE_PARM)
                  {
                    if (TEMPLATE_TEMPLATE_PARM_TEMPLATE_INFO (t))
                      {
                        /* We are processing a type constructed from
                           a template template parameter */
                        tree argvec = tsubst (TYPE_TI_ARGS (t),
                                              args, complain, in_decl);
                        if (argvec == error_mark_node)
                          return error_mark_node;
                        
                        /* We can get a TEMPLATE_TEMPLATE_PARM here when 
                           we are resolving nested-types in the signature of 
                           a member function templates.
                           Otherwise ARG is a TEMPLATE_DECL and is the real 
                           template to be instantiated.  */
                        if (TREE_CODE (arg) == TEMPLATE_TEMPLATE_PARM)
                          arg = TYPE_NAME (arg);

                        r = lookup_template_class (DECL_NAME (arg), 
                                                   argvec, in_decl, 
                                                   DECL_CONTEXT (arg),
                                                   /*entering_scope=*/0);
                        return cp_build_qualified_type (r, TYPE_QUALS (t));
                      }
                    else
                      /* We are processing a template argument list.  */ 
                      return arg;
                  }
                else
                  return arg;
              }
          }
        else
          my_friendly_abort (981018);

        if (level == 1)
          /* This can happen during the attempted tsubst'ing in
             unify.  This means that we don't yet have any information
             about the template parameter in question.  */
          return t;

        /* If we get here, we must have been looking at a parm for a
           more deeply nested template.  Make a new version of this
           template parameter, but with a lower level.  */
        switch (TREE_CODE (t))
          {
          case TEMPLATE_TYPE_PARM:
          case TEMPLATE_TEMPLATE_PARM:
            r = copy_node (t);
            TEMPLATE_TYPE_PARM_INDEX (r)
              = reduce_template_parm_level (TEMPLATE_TYPE_PARM_INDEX (t),
                                            r, levels);
            TYPE_STUB_DECL (r) = TYPE_NAME (r) = TEMPLATE_TYPE_DECL (r);
            TYPE_MAIN_VARIANT (r) = r;
            TYPE_POINTER_TO (r) = NULL_TREE;
            TYPE_REFERENCE_TO (r) = NULL_TREE;

            if (TREE_CODE (t) == TEMPLATE_TEMPLATE_PARM
                && TEMPLATE_TEMPLATE_PARM_TEMPLATE_INFO (t))
              {
                tree argvec = tsubst (TYPE_TI_ARGS (t), args,
                                      complain, in_decl); 
                if (argvec == error_mark_node)
                  return error_mark_node;

                TEMPLATE_TEMPLATE_PARM_TEMPLATE_INFO (r)
                  = perm_tree_cons (TYPE_NAME (t), argvec, NULL_TREE);
              }
            break;

          case TEMPLATE_PARM_INDEX:
            r = reduce_template_parm_level (t, type, levels);
            break;
           
          default:
            my_friendly_abort (0);
          }

        return r;
      }

    case TREE_LIST:
      {
        tree purpose, value, chain, result;
        int via_public, via_virtual, via_protected;

        if (t == void_list_node)
          return t;

        via_public = TREE_VIA_PUBLIC (t);
        via_protected = TREE_VIA_PROTECTED (t);
        via_virtual = TREE_VIA_VIRTUAL (t);

        purpose = TREE_PURPOSE (t);
        if (purpose)
          {
            purpose = tsubst (purpose, args, complain, in_decl);
            if (purpose == error_mark_node)
              return error_mark_node;
          }
        value = TREE_VALUE (t);
        if (value)
          {
            value = tsubst (value, args, complain, in_decl);
            if (value == error_mark_node)
              return error_mark_node;
          }
        chain = TREE_CHAIN (t);
        if (chain && chain != void_type_node)
          {
            chain = tsubst (chain, args, complain, in_decl);
            if (chain == error_mark_node)
              return error_mark_node;
          }
        if (purpose == TREE_PURPOSE (t)
            && value == TREE_VALUE (t)
            && chain == TREE_CHAIN (t))
          return t;
        result = hash_tree_cons (via_public, via_virtual, via_protected,
                                 purpose, value, chain);
        TREE_PARMLIST (result) = TREE_PARMLIST (t);
        return result;
      }
    case TREE_VEC:
      if (type != NULL_TREE)
        {
          /* A binfo node.  We always need to make a copy, of the node
             itself and of its BINFO_BASETYPES.  */

          t = copy_node (t);

          /* Make sure type isn't a typedef copy.  */
          type = BINFO_TYPE (TYPE_BINFO (type));

          TREE_TYPE (t) = complete_type (type);
          if (IS_AGGR_TYPE (type))
            {
              BINFO_VTABLE (t) = TYPE_BINFO_VTABLE (type);
              BINFO_VIRTUALS (t) = TYPE_BINFO_VIRTUALS (type);
              if (TYPE_BINFO_BASETYPES (type) != NULL_TREE)
                BINFO_BASETYPES (t) = copy_node (TYPE_BINFO_BASETYPES (type));
            }
          return t;
        }

      /* Otherwise, a vector of template arguments.  */
      return tsubst_template_arg_vector (t, args, complain);

    case POINTER_TYPE:
    case REFERENCE_TYPE:
      {
        enum tree_code code;

        if (type == TREE_TYPE (t))
          return t;

        code = TREE_CODE (t);


        /* [temp.deduct]
           
           Type deduction may fail for any of the following
           reasons:  

           -- Attempting to create a pointer to reference type.
           -- Attempting to create a reference to a reference type or
              a reference to void.  */
        if (TREE_CODE (type) == REFERENCE_TYPE
            || (code == REFERENCE_TYPE && TREE_CODE (type) == VOID_TYPE))
          {
            static int   last_line = 0;
            static char* last_file = 0;

            /* We keep track of the last time we issued this error
               message to avoid spewing a ton of messages during a
               single bad template instantiation.  */
            if (complain && (last_line != lineno ||
                             last_file != input_filename))
              {
                if (TREE_CODE (type) == VOID_TYPE)
                  cp_error ("forming reference to void");
                else
                  cp_error ("forming %s to reference type `%T'",
                            (code == POINTER_TYPE) ? "pointer" : "reference",
                            type);
                last_line = lineno;
                last_file = input_filename;
              }

            return error_mark_node;
          }
        else if (code == POINTER_TYPE)
          r = build_pointer_type (type);
        else
          r = build_reference_type (type);
        r = cp_build_qualified_type (r, TYPE_QUALS (t));

        /* Will this ever be needed for TYPE_..._TO values?  */
        layout_type (r);
        return r;
      }
    case OFFSET_TYPE:
      {
        r = tsubst (TYPE_OFFSET_BASETYPE (t), args, complain, in_decl);
        if (r == error_mark_node || !IS_AGGR_TYPE (r))
          {
            /* [temp.deduct]

               Type deduction may fail for any of the following
               reasons:
               
               -- Attempting to create "pointer to member of T" when T
                  is not a class type.  */
            if (complain)
              cp_error ("creating pointer to member of non-class type `%T'", 
                        r);
            return error_mark_node;
          }
        return build_offset_type (r, type);
      }
    case FUNCTION_TYPE:
    case METHOD_TYPE:
      {
        tree fntype;
        tree raises;

        fntype = tsubst_function_type (t, args, complain, in_decl);
        if (fntype == error_mark_node)
          return error_mark_node;

        /* Substitue the exception specification. */
        raises = TYPE_RAISES_EXCEPTIONS (t);
        if (raises)
          {
            raises = tsubst (raises, args, complain, in_decl);
            if (raises == error_mark_node)
              return raises;
            fntype = build_exception_variant (fntype, raises);
          }
        return fntype;
      }
    case ARRAY_TYPE:
      {
        tree domain = tsubst (TYPE_DOMAIN (t), args, complain, in_decl);
        if (domain == error_mark_node)
          return error_mark_node;

        /* As an optimization, we avoid regenerating the array type if
           it will obviously be the same as T.  */
        if (type == TREE_TYPE (t) && domain == TYPE_DOMAIN (t))
          return t;

        /* These checks should match the ones in grokdeclarator.  

           [temp.deduct] 
        
           The deduction may fail for any of the following reasons: 

           -- Attempting to create an array with an element type that
              is void, a function type, or a reference type.  */
        if (TREE_CODE (type) == VOID_TYPE 
            || TREE_CODE (type) == FUNCTION_TYPE
            || TREE_CODE (type) == REFERENCE_TYPE)
          {
            if (complain)
              cp_error ("creating array of `%T'", type);
            return error_mark_node;
          }

        r = build_cplus_array_type (type, domain);
        return r;
      }

    case PLUS_EXPR:
    case MINUS_EXPR:
      {
        tree e1 = tsubst (TREE_OPERAND (t, 0), args, complain,
                          in_decl);
        tree e2 = tsubst (TREE_OPERAND (t, 1), args, complain,
                          in_decl);

        if (e1 == error_mark_node || e2 == error_mark_node)
          return error_mark_node;

        return fold (build (TREE_CODE (t), TREE_TYPE (t), e1, e2));
      }

    case NEGATE_EXPR:
    case NOP_EXPR:
      {
        tree e = tsubst (TREE_OPERAND (t, 0), args, complain,
                          in_decl);
        if (e == error_mark_node)
          return error_mark_node;

        return fold (build (TREE_CODE (t), TREE_TYPE (t), e));
      }

    case TYPENAME_TYPE:
      {
        tree ctx = tsubst_aggr_type (TYPE_CONTEXT (t), args, complain,
                                     in_decl, /*entering_scope=*/1);
        tree f = tsubst_copy (TYPENAME_TYPE_FULLNAME (t), args,
                              complain, in_decl); 

        if (ctx == error_mark_node || f == error_mark_node)
          return error_mark_node;

        if (!IS_AGGR_TYPE (ctx))
          {
            if (complain)
              cp_error ("`%T' is not a class, struct, or union type",
                        ctx);
            return error_mark_node;
          }
        else if (!uses_template_parms (ctx) && !TYPE_BEING_DEFINED (ctx))
          {
            /* Normally, make_typename_type does not require that the CTX
               have complete type in order to allow things like:
             
                 template <class T> struct S { typename S<T>::X Y; };

               But, such constructs have already been resolved by this
               point, so here CTX really should have complete type, unless
               it's a partial instantiation.  */
            ctx = complete_type (ctx);
            if (!TYPE_SIZE (ctx))
              {
                if (complain)
                  incomplete_type_error (NULL_TREE, ctx);
                return error_mark_node;
              }
          }

        f = make_typename_type (ctx, f);
        return cp_build_qualified_type (f, 
                                        CP_TYPE_QUALS (f) 
                                        | CP_TYPE_QUALS (t));
      }

    case INDIRECT_REF:
      {
        tree e = tsubst (TREE_OPERAND (t, 0), args, complain,
                         in_decl);
        if (e == error_mark_node)
          return error_mark_node;
        return make_pointer_declarator (type, e);
      }

    case ADDR_EXPR:
      {
        tree e = tsubst (TREE_OPERAND (t, 0), args, complain,
                         in_decl);
        if (e == error_mark_node)
          return error_mark_node;
        return make_reference_declarator (type, e);
      }

    case ARRAY_REF:
      {
        tree e1 = tsubst (TREE_OPERAND (t, 0), args, complain,
                          in_decl);
        tree e2 = tsubst_expr (TREE_OPERAND (t, 1), args, complain,
                               in_decl);
        if (e1 == error_mark_node || e2 == error_mark_node)
          return error_mark_node;

        return build_parse_node (ARRAY_REF, e1, e2, tsubst_expr);
      }

    case CALL_EXPR:
      {
        tree e1 = tsubst (TREE_OPERAND (t, 0), args, complain,
                          in_decl);
        tree e2 = tsubst_call_declarator_parms (TREE_OPERAND (t, 1), args, 
                                                complain, in_decl);
        tree e3 = tsubst (TREE_TYPE (t), args, complain, in_decl);

        if (e1 == error_mark_node || e2 == error_mark_node 
            || e3 == error_mark_node)
          return error_mark_node;

        return make_call_declarator (e1, e2, TREE_OPERAND (t, 2), e3);
      }

    case SCOPE_REF:
      {
        tree e1 = tsubst (TREE_OPERAND (t, 0), args, complain,
                                  in_decl);
        tree e2 = tsubst (TREE_OPERAND (t, 1), args, complain, in_decl);
        if (e1 == error_mark_node || e2 == error_mark_node)
          return error_mark_node;

        return build_parse_node (TREE_CODE (t), e1, e2);
      }

    case TYPEOF_TYPE:
      {
        tree e1 = tsubst_expr (TYPE_FIELDS (t), args, complain,
                               in_decl);
        if (e1 == error_mark_node)
          return error_mark_node;

        return TREE_TYPE (e1); 
      }

    default:
      sorry ("use of `%s' in template",
             tree_code_name [(int) TREE_CODE (t)]);
      return error_mark_node;
    }
}

void
do_pushlevel ()
{
  emit_line_note (input_filename, lineno);
  pushlevel (0);
  clear_last_expr ();
  push_momentary ();
  expand_start_bindings (0);
}  

tree
do_poplevel ()
{
  tree t;
  int saved_warn_unused = 0;

  if (processing_template_decl)
    {
      saved_warn_unused = warn_unused;
      warn_unused = 0;
    }
  expand_end_bindings (getdecls (), kept_level_p (), 0);
  if (processing_template_decl)
    warn_unused = saved_warn_unused;
  t = poplevel (kept_level_p (), 1, 0);
  pop_momentary ();
  return t;
}

/* Like tsubst, but deals with expressions.  This function just replaces
   template parms; to finish processing the resultant expression, use
   tsubst_expr.  */

tree
tsubst_copy (t, args, complain, in_decl)
     tree t, args;
     int complain;
     tree in_decl;
{
  enum tree_code code;
  tree r;

  if (t == NULL_TREE || t == error_mark_node)
    return t;

  code = TREE_CODE (t);

  switch (code)
    {
    case PARM_DECL:
      return do_identifier (DECL_NAME (t), 0, NULL_TREE);

    case CONST_DECL:
      {
        tree enum_type;
        tree v;

        if (!DECL_CONTEXT (t))
          /* This is a global enumeration constant.  */
          return t;

        /* Unfortunately, we cannot just call lookup_name here.
         Consider:

         template <int I> int f() {
           enum E { a = I };
           struct S { void g() { E e = a; } };
         };

         When we instantiate f<7>::S::g(), say, lookup_name is not
         clever enough to find f<7>::a.  */
        enum_type 
          = tsubst_aggr_type (TREE_TYPE (t), args, complain, in_decl, 
                              /*entering_scope=*/0);

        for (v = TYPE_VALUES (enum_type); 
             v != NULL_TREE; 
             v = TREE_CHAIN (v))
          if (TREE_PURPOSE (v) == DECL_NAME (t))
            return TREE_VALUE (v);

          /* We didn't find the name.  That should never happen; if
             name-lookup found it during preliminary parsing, we
             should find it again here during instantiation.  */
        my_friendly_abort (0);
      }
      return t;

    case FIELD_DECL:
      if (DECL_CONTEXT (t))
        {
          tree ctx;

          ctx = tsubst_aggr_type (DECL_CONTEXT (t), args, complain, in_decl,
                                  /*entering_scope=*/1);
          if (ctx != DECL_CONTEXT (t))
            return lookup_field (ctx, DECL_NAME (t), 0, 0);
        }
      return t;

    case VAR_DECL:
    case FUNCTION_DECL:
      if (DECL_LANG_SPECIFIC (t) && DECL_TEMPLATE_INFO (t))
        t = tsubst (t, args, complain, in_decl);
      mark_used (t);
      return t;

    case TEMPLATE_DECL:
      if (is_member_template (t))
        return tsubst (t, args, complain, in_decl);
      else
        return t;

    case LOOKUP_EXPR:
      {
        /* We must tsbust into a LOOKUP_EXPR in case the names to
           which it refers is a conversion operator; in that case the
           name will change.  We avoid making unnecessary copies,
           however.  */
        
        tree id = tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl);

        if (id != TREE_OPERAND (t, 0))
          {
            r = build_nt (LOOKUP_EXPR, id);
            LOOKUP_EXPR_GLOBAL (r) = LOOKUP_EXPR_GLOBAL (t);
            t = r;
          }

        return t;
      }

    case CAST_EXPR:
    case REINTERPRET_CAST_EXPR:
    case CONST_CAST_EXPR:
    case STATIC_CAST_EXPR:
    case DYNAMIC_CAST_EXPR:
    case NOP_EXPR:
      return build1
        (code, tsubst (TREE_TYPE (t), args, complain, in_decl),
         tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl));

    case INDIRECT_REF:
    case PREDECREMENT_EXPR:
    case PREINCREMENT_EXPR:
    case POSTDECREMENT_EXPR:
    case POSTINCREMENT_EXPR:
    case NEGATE_EXPR:
    case TRUTH_NOT_EXPR:
    case BIT_NOT_EXPR:
    case ADDR_EXPR:
    case CONVERT_EXPR:      /* Unary + */
    case SIZEOF_EXPR:
    case ALIGNOF_EXPR:
    case ARROW_EXPR:
    case THROW_EXPR:
    case TYPEID_EXPR:
      return build1
        (code, NULL_TREE,
         tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl));

    case PLUS_EXPR:
    case MINUS_EXPR:
    case MULT_EXPR:
    case TRUNC_DIV_EXPR:
    case CEIL_DIV_EXPR:
    case FLOOR_DIV_EXPR:
    case ROUND_DIV_EXPR:
    case EXACT_DIV_EXPR:
    case BIT_AND_EXPR:
    case BIT_ANDTC_EXPR:
    case BIT_IOR_EXPR:
    case BIT_XOR_EXPR:
    case TRUNC_MOD_EXPR:
    case FLOOR_MOD_EXPR:
    case TRUTH_ANDIF_EXPR:
    case TRUTH_ORIF_EXPR:
    case TRUTH_AND_EXPR:
    case TRUTH_OR_EXPR:
    case RSHIFT_EXPR:
    case LSHIFT_EXPR:
    case RROTATE_EXPR:
    case LROTATE_EXPR:
    case EQ_EXPR:
    case NE_EXPR:
    case MAX_EXPR:
    case MIN_EXPR:
    case LE_EXPR:
    case GE_EXPR:
    case LT_EXPR:
    case GT_EXPR:
    case COMPONENT_REF:
    case ARRAY_REF:
    case COMPOUND_EXPR:
    case SCOPE_REF:
    case DOTSTAR_EXPR:
    case MEMBER_REF:
      return build_nt
        (code, tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, complain, in_decl));

    case CALL_EXPR:
      {
        tree fn = TREE_OPERAND (t, 0);
        if (is_overloaded_fn (fn))
          fn = tsubst_copy (get_first_fn (fn), args, complain, in_decl);
        else
          /* Sometimes FN is a LOOKUP_EXPR.  */
          fn = tsubst_copy (fn, args, complain, in_decl);
        return build_nt
          (code, fn, tsubst_copy (TREE_OPERAND (t, 1), args, complain,
                                  in_decl),
           NULL_TREE);
      }

    case METHOD_CALL_EXPR:
      {
        tree name = TREE_OPERAND (t, 0);
        if (TREE_CODE (name) == BIT_NOT_EXPR)
          {
            name = tsubst_copy (TREE_OPERAND (name, 0), args,
                                complain, in_decl);
            name = build1 (BIT_NOT_EXPR, NULL_TREE, name);
          }
        else if (TREE_CODE (name) == SCOPE_REF
                 && TREE_CODE (TREE_OPERAND (name, 1)) == BIT_NOT_EXPR)
          {
            tree base = tsubst_copy (TREE_OPERAND (name, 0), args,
                                     complain, in_decl);
            name = TREE_OPERAND (name, 1);
            name = tsubst_copy (TREE_OPERAND (name, 0), args,
                                complain, in_decl);
            name = build1 (BIT_NOT_EXPR, NULL_TREE, name);
            name = build_nt (SCOPE_REF, base, name);
          }
        else
          name = tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl);
        return build_nt
          (code, name, tsubst_copy (TREE_OPERAND (t, 1), args,
                                    complain, in_decl),
           tsubst_copy (TREE_OPERAND (t, 2), args, complain, in_decl),
           NULL_TREE);
      }

    case BIND_EXPR:
    case COND_EXPR:
    case MODOP_EXPR:
      {
        r = build_nt
          (code, tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl),
           tsubst_copy (TREE_OPERAND (t, 1), args, complain, in_decl),
           tsubst_copy (TREE_OPERAND (t, 2), args, complain, in_decl));

        if (code == BIND_EXPR && !processing_template_decl)
          {
            /* This processing should really occur in tsubst_expr,
               However, tsubst_expr does not recurse into expressions,
               since it assumes that there aren't any statements
               inside them.  Instead, it simply calls
               build_expr_from_tree.  So, we need to expand the
               BIND_EXPR here.  */ 
            tree rtl_expr = begin_stmt_expr ();
            tree block = tsubst_expr (TREE_OPERAND (r, 1), args,
                                      complain, in_decl);
            r = finish_stmt_expr (rtl_expr, block);
          }

        return r;
      }

    case NEW_EXPR:
      {
        r = build_nt
        (code, tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, complain, in_decl),
         tsubst_copy (TREE_OPERAND (t, 2), args, complain, in_decl));
        NEW_EXPR_USE_GLOBAL (r) = NEW_EXPR_USE_GLOBAL (t);
        return r;
      }

    case DELETE_EXPR:
      {
        r = build_nt
        (code, tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, complain, in_decl));
        DELETE_EXPR_USE_GLOBAL (r) = DELETE_EXPR_USE_GLOBAL (t);
        DELETE_EXPR_USE_VEC (r) = DELETE_EXPR_USE_VEC (t);
        return r;
      }

    case TEMPLATE_ID_EXPR:
      {
        /* Substituted template arguments */
        tree targs = tsubst_copy (TREE_OPERAND (t, 1), args, complain,
                                  in_decl);
        tree chain;
        for (chain = targs; chain; chain = TREE_CHAIN (chain))
          TREE_VALUE (chain) = maybe_fold_nontype_arg (TREE_VALUE (chain));

        return lookup_template_function
          (tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl), targs);
      }

    case TREE_LIST:
      {
        tree purpose, value, chain;

        if (t == void_list_node)
          return t;

        purpose = TREE_PURPOSE (t);
        if (purpose)
          purpose = tsubst_copy (purpose, args, complain, in_decl);
        value = TREE_VALUE (t);
        if (value)
          value = tsubst_copy (value, args, complain, in_decl);
        chain = TREE_CHAIN (t);
        if (chain && chain != void_type_node)
          chain = tsubst_copy (chain, args, complain, in_decl);
        if (purpose == TREE_PURPOSE (t)
            && value == TREE_VALUE (t)
            && chain == TREE_CHAIN (t))
          return t;
        return tree_cons (purpose, value, chain);
      }

    case RECORD_TYPE:
    case UNION_TYPE:
    case ENUMERAL_TYPE:
    case INTEGER_TYPE:
    case TEMPLATE_TYPE_PARM:
    case TEMPLATE_TEMPLATE_PARM:
    case TEMPLATE_PARM_INDEX:
    case POINTER_TYPE:
    case REFERENCE_TYPE:
    case OFFSET_TYPE:
    case FUNCTION_TYPE:
    case METHOD_TYPE:
    case ARRAY_TYPE:
    case TYPENAME_TYPE:
    case TYPE_DECL:
      return tsubst (t, args, complain, in_decl);

    case IDENTIFIER_NODE:
      if (IDENTIFIER_TYPENAME_P (t)
          /* Make sure it's not just a variable named `__opr', for instance,
             which can occur in some existing code.  */
          && TREE_TYPE (t))
        return build_typename_overload
          (tsubst (TREE_TYPE (t), args, complain, in_decl));
      else
        return t;

    case CONSTRUCTOR:
      {
        r = build
          (CONSTRUCTOR, tsubst (TREE_TYPE (t), args, complain, in_decl), 
           NULL_TREE, tsubst_copy (CONSTRUCTOR_ELTS (t), args,
                                   complain, in_decl));
        TREE_HAS_CONSTRUCTOR (r) = TREE_HAS_CONSTRUCTOR (t);
        return r;
      }

    default:
      return t;
    }
}

/* Like tsubst_copy, but also does semantic processing and RTL expansion.  */

tree
tsubst_expr (t, args, complain, in_decl)
     tree t, args;
     int complain;
     tree in_decl;
{
  if (t == NULL_TREE || t == error_mark_node)
    return t;

  if (processing_template_decl)
    return tsubst_copy (t, args, complain, in_decl);

  switch (TREE_CODE (t))
    {
    case RETURN_STMT:
      lineno = TREE_COMPLEXITY (t);
      finish_return_stmt (tsubst_expr (RETURN_EXPR (t),
                                       args, complain, in_decl));
      break;

    case EXPR_STMT:
      lineno = TREE_COMPLEXITY (t);
      finish_expr_stmt (tsubst_expr (EXPR_STMT_EXPR (t),
                                     args, complain, in_decl));
      break;

    case DECL_STMT:
      {
        int i = suspend_momentary ();
        tree dcl, init;

        lineno = TREE_COMPLEXITY (t);
        emit_line_note (input_filename, lineno);
        dcl = start_decl
          (tsubst (TREE_OPERAND (t, 0), args, complain, in_decl),
           tsubst (TREE_OPERAND (t, 1), args, complain, in_decl),
           TREE_OPERAND (t, 2) != 0, NULL_TREE, NULL_TREE);
        init = tsubst_expr (TREE_OPERAND (t, 2), args, complain, in_decl);
        cp_finish_decl
          (dcl, init, NULL_TREE, 1, /*init ? LOOKUP_ONLYCONVERTING :*/ 0);
        resume_momentary (i);
        return dcl;
      }

    case FOR_STMT:
      {
        tree tmp;
        lineno = TREE_COMPLEXITY (t);

        begin_for_stmt ();
        for (tmp = FOR_INIT_STMT (t); tmp; tmp = TREE_CHAIN (tmp))
          tsubst_expr (tmp, args, complain, in_decl);
        finish_for_init_stmt (NULL_TREE);
        finish_for_cond (tsubst_expr (FOR_COND (t), args,
                                      complain, in_decl),
                         NULL_TREE);
        tmp = tsubst_expr (FOR_EXPR (t), args, complain, in_decl);
        finish_for_expr (tmp, NULL_TREE);
        tsubst_expr (FOR_BODY (t), args, complain, in_decl);
        finish_for_stmt (tmp, NULL_TREE);
      }
      break;

    case WHILE_STMT:
      {
        lineno = TREE_COMPLEXITY (t);
        begin_while_stmt ();
        finish_while_stmt_cond (tsubst_expr (WHILE_COND (t),
                                             args, complain, in_decl),
                                NULL_TREE);
        tsubst_expr (WHILE_BODY (t), args, complain, in_decl);
        finish_while_stmt (NULL_TREE);
      }
      break;

    case DO_STMT:
      {
        lineno = TREE_COMPLEXITY (t);
        begin_do_stmt ();
        tsubst_expr (DO_BODY (t), args, complain, in_decl);
        finish_do_body (NULL_TREE);
        finish_do_stmt (tsubst_expr (DO_COND (t), args,
                                     complain, in_decl),
                        NULL_TREE);
      }
      break;

    case IF_STMT:
      {
        tree tmp;

        lineno = TREE_COMPLEXITY (t);
        begin_if_stmt ();
        finish_if_stmt_cond (tsubst_expr (IF_COND (t),
                                          args, complain, in_decl),
                             NULL_TREE);

        if (tmp = THEN_CLAUSE (t), tmp)
          {
            tsubst_expr (tmp, args, complain, in_decl);
            finish_then_clause (NULL_TREE);
          }

        if (tmp = ELSE_CLAUSE (t), tmp)
          {
            begin_else_clause ();
            tsubst_expr (tmp, args, complain, in_decl);
            finish_else_clause (NULL_TREE);
          }

        finish_if_stmt ();
      }
      break;

    case COMPOUND_STMT:
      {
        tree substmt;

        lineno = TREE_COMPLEXITY (t);
        begin_compound_stmt (COMPOUND_STMT_NO_SCOPE (t));
        for (substmt = COMPOUND_BODY (t); 
             substmt != NULL_TREE;
             substmt = TREE_CHAIN (substmt))
          tsubst_expr (substmt, args, complain, in_decl);
        return finish_compound_stmt (COMPOUND_STMT_NO_SCOPE (t), 
                                     NULL_TREE);
      }
      break;

    case BREAK_STMT:
      lineno = TREE_COMPLEXITY (t);
      finish_break_stmt ();
      break;

    case CONTINUE_STMT:
      lineno = TREE_COMPLEXITY (t);
      finish_continue_stmt ();
      break;

    case SWITCH_STMT:
      {
        tree val, tmp;

        lineno = TREE_COMPLEXITY (t);
        begin_switch_stmt ();
        val = tsubst_expr (SWITCH_COND (t), args, complain, in_decl);
        finish_switch_cond (val);
        
        if (tmp = TREE_OPERAND (t, 1), tmp)
          tsubst_expr (tmp, args, complain, in_decl);

        finish_switch_stmt (val, NULL_TREE);
      }
      break;

    case CASE_LABEL:
      finish_case_label (tsubst_expr (CASE_LOW (t), args, complain, in_decl),
                         tsubst_expr (CASE_HIGH (t), args, complain, in_decl));
      break;

    case LABEL_DECL:
      t = define_label (DECL_SOURCE_FILE (t), DECL_SOURCE_LINE (t),
                        DECL_NAME (t));
      if (t)
        expand_label (t);
      break;

    case GOTO_STMT:
      lineno = TREE_COMPLEXITY (t);
      t = GOTO_DESTINATION (t);
      if (TREE_CODE (t) != IDENTIFIER_NODE)
        /* Computed goto's must be tsubst'd into.  On the other hand,
           non-computed gotos must not be; the identifier in question
           will have no binding.  */
        t = tsubst_expr (t, args, complain, in_decl);
      finish_goto_stmt (t);
      break;

    case ASM_STMT:
      lineno = TREE_COMPLEXITY (t);
      finish_asm_stmt (tsubst_expr (ASM_CV_QUAL (t), args, complain, in_decl),
                       tsubst_expr (ASM_STRING (t), args, complain, in_decl),
                       tsubst_expr (ASM_OUTPUTS (t), args, complain, in_decl),
                       tsubst_expr (ASM_INPUTS (t), args, complain, in_decl), 
                       tsubst_expr (ASM_CLOBBERS (t), args, complain,
                                    in_decl));
      break;

    case TRY_BLOCK:
      lineno = TREE_COMPLEXITY (t);
      begin_try_block ();
      tsubst_expr (TRY_STMTS (t), args, complain, in_decl);
      finish_try_block (NULL_TREE);
      {
        tree handler = TRY_HANDLERS (t);
        for (; handler; handler = TREE_CHAIN (handler))
          tsubst_expr (handler, args, complain, in_decl);
      }
      finish_handler_sequence (NULL_TREE);
      break;

    case HANDLER:
      lineno = TREE_COMPLEXITY (t);
      begin_handler ();
      if (HANDLER_PARMS (t))
        {
          tree d = HANDLER_PARMS (t);
          expand_start_catch_block
            (tsubst (TREE_OPERAND (d, 1), args, complain, in_decl),
             tsubst (TREE_OPERAND (d, 0), args, complain, in_decl));
        }
      else
        expand_start_catch_block (NULL_TREE, NULL_TREE);
      finish_handler_parms (NULL_TREE);
      tsubst_expr (HANDLER_BODY (t), args, complain, in_decl);
      finish_handler (NULL_TREE);
      break;

    case TAG_DEFN:
      lineno = TREE_COMPLEXITY (t);
      t = TREE_TYPE (t);
      if (TREE_CODE (t) == ENUMERAL_TYPE)
        tsubst (t, args, complain, NULL_TREE);
      break;

    default:
      return build_expr_from_tree (tsubst_copy (t, args, complain, in_decl));
    }
  return NULL_TREE;
}

/* Instantiate the indicated variable or function template TMPL with
   the template arguments in TARG_PTR.  */

tree
instantiate_template (tmpl, targ_ptr)
     tree tmpl, targ_ptr;
{
  tree fndecl;
  tree gen_tmpl;
  tree spec;
  int i, len;
  struct obstack *old_fmp_obstack;
  extern struct obstack *function_maybepermanent_obstack;
  tree inner_args;

  if (tmpl == error_mark_node)
    return error_mark_node;

  my_friendly_assert (TREE_CODE (tmpl) == TEMPLATE_DECL, 283);

  /* Check to see if we already have this specialization.  */
  spec = retrieve_specialization (tmpl, targ_ptr);
  if (spec != NULL_TREE)
    return spec;

  if (DECL_TEMPLATE_INFO (tmpl))
    {
      /* The TMPL is a partial instantiation.  To get a full set of
         arguments we must add the arguments used to perform the
         partial instantiation.  */
      targ_ptr = add_outermost_template_args (DECL_TI_ARGS (tmpl),
                                              targ_ptr);
      gen_tmpl = most_general_template (tmpl);

      /* Check to see if we already have this specialization.  */
      spec = retrieve_specialization (gen_tmpl, targ_ptr);
      if (spec != NULL_TREE)
        return spec;
    }
  else
    gen_tmpl = tmpl;

  push_obstacks (&permanent_obstack, &permanent_obstack);
  old_fmp_obstack = function_maybepermanent_obstack;
  function_maybepermanent_obstack = &permanent_obstack;

  len = DECL_NTPARMS (gen_tmpl);
  inner_args = innermost_args (targ_ptr);
  i = len;
  while (i--)
    {
      tree t = TREE_VEC_ELT (inner_args, i);
      if (TREE_CODE_CLASS (TREE_CODE (t)) == 't')
        {
          tree nt = target_type (t);
          if (IS_AGGR_TYPE (nt) && decl_function_context (TYPE_MAIN_DECL (nt)))
            {
              cp_error ("type `%T' composed from a local class is not a valid template-argument", t);
              cp_error ("  trying to instantiate `%D'", gen_tmpl);
              fndecl = error_mark_node;
              goto out;
            }
        }
    }
  targ_ptr = copy_to_permanent (targ_ptr);

  /* substitute template parameters */
  fndecl = tsubst (DECL_RESULT (gen_tmpl), targ_ptr, /*complain=*/1, gen_tmpl);
  /* The DECL_TI_TEMPLATE should always be the immediate parent
     template, not the most general template.  */
  DECL_TI_TEMPLATE (fndecl) = tmpl;

  if (flag_external_templates)
    add_pending_template (fndecl);

 out:
  function_maybepermanent_obstack = old_fmp_obstack;
  pop_obstacks ();

  return fndecl;
}

/* Push the name of the class template into the scope of the instantiation.  */

void
overload_template_name (type)
     tree type;
{
  tree id = DECL_NAME (CLASSTYPE_TI_TEMPLATE (type));
  tree decl;

  if (IDENTIFIER_CLASS_VALUE (id)
      && TREE_TYPE (IDENTIFIER_CLASS_VALUE (id)) == type)
    return;

  decl = build_decl (TYPE_DECL, id, type);
  SET_DECL_ARTIFICIAL (decl);
  pushdecl_class_level (decl);
}

/* The FN is a TEMPLATE_DECL for a function.  The ARGS are the
   arguments that are being used when calling it.  TARGS is a vector
   into which the deduced template arguments are placed.  

   Return zero for success, 2 for an incomplete match that doesn't resolve
   all the types, and 1 for complete failure.  An error message will be
   printed only for an incomplete match.

   If FN is a conversion operator, RETURN_TYPE is the type desired as
   the result of the conversion operator.

   TPARMS is a vector of template parameters.

   The EXPLICIT_TARGS are explicit template arguments provided via a
   template-id.

   The parameter STRICT is one of:

   DEDUCE_CALL: 
     We are deducing arguments for a function call, as in
     [temp.deduct.call].

   DEDUCE_CONV:
     We are deducing arguments for a conversion function, as in 
     [temp.deduct.conv].

   DEDUCE_EXACT:
     We are deducing arguments when calculating the partial
     ordering between specializations of function or class
     templates, as in [temp.func.order] and [temp.class.order],
     when doing an explicit instantiation as in [temp.explicit],
     when determining an explicit specialization as in
     [temp.expl.spec], or when taking the address of a function
     template, as in [temp.deduct.funcaddr]. 

   The other arguments are as for type_unification.  */

int
fn_type_unification (fn, explicit_targs, targs, args, return_type,
                     strict)
     tree fn, explicit_targs, targs, args, return_type;
     unification_kind_t strict;
{
  tree parms;
  tree fntype;

  my_friendly_assert (TREE_CODE (fn) == TEMPLATE_DECL, 0);
  
  fntype = TREE_TYPE (fn);
  if (explicit_targs)
    {
      /* [temp.deduct]
          
         The specified template arguments must match the template
         parameters in kind (i.e., type, nontype, template), and there
         must not be more arguments than there are parameters;
         otherwise type deduction fails.

         Nontype arguments must match the types of the corresponding
         nontype template parameters, or must be convertible to the
         types of the corresponding nontype parameters as specified in
         _temp.arg.nontype_, otherwise type deduction fails.

         All references in the function type of the function template
         to the corresponding template parameters are replaced by the
         specified template argument values.  If a substitution in a
         template parameter or in the function type of the function
         template results in an invalid type, type deduction fails.  */
      int i;
      tree converted_args;

      converted_args
        = (coerce_template_parms (DECL_INNERMOST_TEMPLATE_PARMS (fn), 
                                  explicit_targs, NULL_TREE, /*complain=*/0, 
                                  /*require_all_arguments=*/0));
      if (converted_args == error_mark_node)
        return 1;

      fntype = tsubst (fntype, converted_args, /*complain=*/0, NULL_TREE);
      if (fntype == error_mark_node)
        return 1;

      /* Place the explicitly specified arguments in TARGS.  */
      for (i = 0; i < TREE_VEC_LENGTH (targs); i++)
        TREE_VEC_ELT (targs, i) = TREE_VEC_ELT (converted_args, i);
    }
     
  parms = TYPE_ARG_TYPES (fntype);

  if (DECL_CONV_FN_P (fn))
    {
      /* This is a template conversion operator.  Use the return types
         as well as the argument types.  */
      parms = scratch_tree_cons (NULL_TREE, TREE_TYPE (fntype),
                                 parms);
      args = scratch_tree_cons (NULL_TREE, return_type, args);
    }

  /* We allow incomplete unification without an error message here
     because the standard doesn't seem to explicitly prohibit it.  Our
     callers must be ready to deal with unification failures in any
     event.  */
  return type_unification_real (DECL_INNERMOST_TEMPLATE_PARMS (fn), 
                                targs, parms, args, /*subr=*/0,
                                strict, /*allow_incomplete*/1);
}

/* Adjust types before performing type deduction, as described in
   [temp.deduct.call] and [temp.deduct.conv].  The rules in these two
   sections are symmetric.  PARM is the type of a function parameter
   or the return type of the conversion function.  ARG is the type of
   the argument passed to the call, or the type of the value
   intialized with the result of the conversion function.  */

static void
maybe_adjust_types_for_deduction (strict, parm, arg)
     unification_kind_t strict;
     tree* parm;
     tree* arg;
{
  switch (strict)
    {
    case DEDUCE_CALL:
      break;

    case DEDUCE_CONV:
      {
        /* Swap PARM and ARG throughout the remainder of this
           function; the handling is precisely symmetric since PARM
           will initialize ARG rather than vice versa.  */
        tree* temp = parm;
        parm = arg;
        arg = temp;
        break;
      }

    case DEDUCE_EXACT:
      /* There is nothing to do in this case.  */
      return;

    default:
      my_friendly_abort (0);
    }

  if (TREE_CODE (*parm) != REFERENCE_TYPE)
    {
      /* [temp.deduct.call]
         
         If P is not a reference type:
         
         --If A is an array type, the pointer type produced by the
         array-to-pointer standard conversion (_conv.array_) is
         used in place of A for type deduction; otherwise,
         
         --If A is a function type, the pointer type produced by
         the function-to-pointer standard conversion
         (_conv.func_) is used in place of A for type deduction;
         otherwise,
         
         --If A is a cv-qualified type, the top level
         cv-qualifiers of A's type are ignored for type
         deduction.  */
      if (TREE_CODE (*arg) == ARRAY_TYPE)
        *arg = build_pointer_type (TREE_TYPE (*arg));
      else if (TREE_CODE (*arg) == FUNCTION_TYPE)
        *arg = build_pointer_type (*arg);
      else
        *arg = TYPE_MAIN_VARIANT (*arg);
    }
  
  /* [temp.deduct.call]
     
     If P is a cv-qualified type, the top level cv-qualifiers
     of P's type are ignored for type deduction.  If P is a
     reference type, the type referred to by P is used for
     type deduction.  */
  *parm = TYPE_MAIN_VARIANT (*parm);
  if (TREE_CODE (*parm) == REFERENCE_TYPE)
    *parm = TREE_TYPE (*parm);
}

/* Like type_unfication.

   If SUBR is 1, we're being called recursively (to unify the
   arguments of a function or method parameter of a function
   template).  */

static int
type_unification_real (tparms, targs, parms, args, subr,
                       strict, allow_incomplete)
     tree tparms, targs, parms, args;
     int subr;
     unification_kind_t strict;
     int allow_incomplete;
{
  tree parm, arg;
  int i;
  int ntparms = TREE_VEC_LENGTH (tparms);
  int sub_strict;

  my_friendly_assert (TREE_CODE (tparms) == TREE_VEC, 289);
  my_friendly_assert (parms == NULL_TREE 
                      || TREE_CODE (parms) == TREE_LIST, 290);
  /* ARGS could be NULL (via a call from parse.y to
     build_x_function_call).  */
  if (args)
    my_friendly_assert (TREE_CODE (args) == TREE_LIST, 291);
  my_friendly_assert (ntparms > 0, 292);

  switch (strict)
    {
    case DEDUCE_CALL:
      sub_strict = UNIFY_ALLOW_MORE_CV_QUAL | UNIFY_ALLOW_DERIVED;
      break;
      
    case DEDUCE_CONV:
      sub_strict = UNIFY_ALLOW_LESS_CV_QUAL;
      break;

    case DEDUCE_EXACT:
      sub_strict = UNIFY_ALLOW_NONE;
      break;
      
    default:
      my_friendly_abort (0);
    }

  while (parms
         && parms != void_list_node
         && args
         && args != void_list_node)
    {
      parm = TREE_VALUE (parms);
      parms = TREE_CHAIN (parms);
      arg = TREE_VALUE (args);
      args = TREE_CHAIN (args);

      if (arg == error_mark_node)
        return 1;
      if (arg == unknown_type_node)
        /* We can't deduce anything from this, but we might get all the
           template args from other function args.  */
        continue;

      /* Conversions will be performed on a function argument that
         corresponds with a function parameter that contains only
         non-deducible template parameters and explicitly specified
         template parameters.  */
      if (! uses_template_parms (parm))
        {
          tree type;

          if (TREE_CODE_CLASS (TREE_CODE (arg)) != 't')
            type = TREE_TYPE (arg);
          else
            {
              type = arg;
              arg = NULL_TREE;
            }

          if (strict == DEDUCE_EXACT)
            {
              if (same_type_p (parm, type))
                continue;
            }
          else
            /* It might work; we shouldn't check now, because we might
               get into infinite recursion.  Overload resolution will
               handle it.  */
            continue;

          return 1;
        }
        
      if (TREE_CODE_CLASS (TREE_CODE (arg)) != 't')
        {
          my_friendly_assert (TREE_TYPE (arg) != NULL_TREE, 293);
          if (type_unknown_p (arg))
            {
              /* [temp.deduct.type] A template-argument can be deduced from
                 a pointer to function or pointer to member function
                 argument if the set of overloaded functions does not
                 contain function templates and at most one of a set of
                 overloaded functions provides a unique match.  */

              if (resolve_overloaded_unification
                  (tparms, targs, parm, arg, strict, sub_strict)
                  != 0)
                return 1;
              continue;
            }
          arg = TREE_TYPE (arg);
        }

      if (!subr)
        maybe_adjust_types_for_deduction (strict, &parm, &arg);

      switch (unify (tparms, targs, parm, arg, sub_strict))
        {
        case 0:
          break;
        case 1:
          return 1;
        }
    }
  /* Fail if we've reached the end of the parm list, and more args
     are present, and the parm list isn't variadic.  */
  if (args && args != void_list_node && parms == void_list_node)
    return 1;
  /* Fail if parms are left and they don't have default values.  */
  if (parms
      && parms != void_list_node
      && TREE_PURPOSE (parms) == NULL_TREE)
    return 1;
  if (!subr)
    for (i = 0; i < ntparms; i++)
      if (TREE_VEC_ELT (targs, i) == NULL_TREE)
        {
          if (!allow_incomplete)
            error ("incomplete type unification");
          return 2;
        }
  return 0;
}

/* Subroutine of type_unification_real.  Args are like the variables at the
   call site.  ARG is an overloaded function (or template-id); we try
   deducing template args from each of the overloads, and if only one
   succeeds, we go with that.  Modifies TARGS and returns 0 on success.  */

static int
resolve_overloaded_unification (tparms, targs, parm, arg, strict,
                                sub_strict)
     tree tparms, targs, parm, arg;
     unification_kind_t strict;
     int sub_strict;
{
  tree tempargs = copy_node (targs);
  int good = 0;

  if (TREE_CODE (arg) == ADDR_EXPR)
    arg = TREE_OPERAND (arg, 0);

  if (TREE_CODE (arg) == COMPONENT_REF)
    /* Handle `&x' where `x' is some static or non-static member
       function name.  */
    arg = TREE_OPERAND (arg, 1);

  /* Strip baselink information.  */
  while (TREE_CODE (arg) == TREE_LIST)
    arg = TREE_VALUE (arg);

  if (TREE_CODE (arg) == TEMPLATE_ID_EXPR)
    {
      /* If we got some explicit template args, we need to plug them into
         the affected templates before we try to unify, in case the
         explicit args will completely resolve the templates in question.  */

      tree expl_subargs = TREE_OPERAND (arg, 1);
      arg = TREE_OPERAND (arg, 0);

      for (; arg; arg = OVL_NEXT (arg))
        {
          tree fn = OVL_CURRENT (arg);
          tree subargs, elem;

          if (TREE_CODE (fn) != TEMPLATE_DECL)
            continue;

          subargs = get_bindings_overload (fn, DECL_RESULT (fn), expl_subargs);
          if (subargs)
            {
              elem = tsubst (TREE_TYPE (fn), subargs, /*complain=*/0,
                             NULL_TREE);
              if (TREE_CODE (elem) == METHOD_TYPE)
                elem = build_ptrmemfunc_type (build_pointer_type (elem));
              good += try_one_overload (tparms, targs, tempargs, parm, elem,
                                        strict, sub_strict);
            }
        }
    }
  else if (TREE_CODE (arg) == OVERLOAD)
    {
      for (; arg; arg = OVL_NEXT (arg))
        {
          tree type = TREE_TYPE (OVL_CURRENT (arg));
          if (TREE_CODE (type) == METHOD_TYPE)
            type = build_ptrmemfunc_type (build_pointer_type (type));
          good += try_one_overload (tparms, targs, tempargs, parm,
                                    type,
                                    strict, sub_strict);
        }
    }
  else
    my_friendly_abort (981006);

  /* [temp.deduct.type] A template-argument can be deduced from a pointer
     to function or pointer to member function argument if the set of
     overloaded functions does not contain function templates and at most
     one of a set of overloaded functions provides a unique match.

     So if we found multiple possibilities, we return success but don't
     deduce anything.  */

  if (good == 1)
    {
      int i = TREE_VEC_LENGTH (targs);
      for (; i--; )
        if (TREE_VEC_ELT (tempargs, i))
          TREE_VEC_ELT (targs, i) = TREE_VEC_ELT (tempargs, i);
    }
  if (good)
    return 0;

  return 1;
}

/* Subroutine of resolve_overloaded_unification; does deduction for a single
   overload.  Fills TARGS with any deduced arguments, or error_mark_node if
   different overloads deduce different arguments for a given parm.
   Returns 1 on success.  */

static int
try_one_overload (tparms, orig_targs, targs, parm, arg, strict,
                  sub_strict)
     tree tparms, orig_targs, targs, parm, arg;
     unification_kind_t strict;
     int sub_strict;
{
  int nargs;
  tree tempargs;
  int i;

  /* [temp.deduct.type] A template-argument can be deduced from a pointer
     to function or pointer to member function argument if the set of
     overloaded functions does not contain function templates and at most
     one of a set of overloaded functions provides a unique match.

     So if this is a template, just return success.  */

  if (uses_template_parms (arg))
    return 1;

  maybe_adjust_types_for_deduction (strict, &parm, &arg);

  /* We don't copy orig_targs for this because if we have already deduced
     some template args from previous args, unify would complain when we
     try to deduce a template parameter for the same argument, even though
     there isn't really a conflict.  */
  nargs = TREE_VEC_LENGTH (targs);
  tempargs = make_scratch_vec (nargs);

  if (unify (tparms, tempargs, parm, arg, sub_strict) != 0)
    return 0;

  /* First make sure we didn't deduce anything that conflicts with
     explicitly specified args.  */
  for (i = nargs; i--; )
    {
      tree elt = TREE_VEC_ELT (tempargs, i);
      tree oldelt = TREE_VEC_ELT (orig_targs, i);

      if (elt == NULL_TREE)
        continue;
      else if (uses_template_parms (elt))
        {
          /* Since we're unifying against ourselves, we will fill in template
             args used in the function parm list with our own template parms.
             Discard them.  */
          TREE_VEC_ELT (tempargs, i) = NULL_TREE;
          continue;
        }
      else if (oldelt && ! template_args_equal (oldelt, elt))
        return 0;
    }

  for (i = nargs; i--; )
    {
      tree elt = TREE_VEC_ELT (tempargs, i);

      if (elt)
        TREE_VEC_ELT (targs, i) = elt;
    }

  return 1;
}

/* PARM is a template class (perhaps with unbound template
   parameters).  ARG is a fully instantiated type.  If ARG can be
   bound to PARM, return ARG, otherwise return NULL_TREE.  TPARMS and
   TARGS are as for unify.  */

static tree
try_class_unification (tparms, targs, parm, arg)
     tree tparms;
     tree targs;
     tree parm;
     tree arg;
{
  int i;
  tree copy_of_targs;

  if (!CLASSTYPE_TEMPLATE_INFO (arg)
      || CLASSTYPE_TI_TEMPLATE (arg) != CLASSTYPE_TI_TEMPLATE (parm))
    return NULL_TREE;

  /* We need to make a new template argument vector for the call to
     unify.  If we used TARGS, we'd clutter it up with the result of
     the attempted unification, even if this class didn't work out.
     We also don't want to commit ourselves to all the unifications
     we've already done, since unification is supposed to be done on
     an argument-by-argument basis.  In other words, consider the
     following pathological case:

       template <int I, int J, int K>
       struct S {};
       
       template <int I, int J>
       struct S<I, J, 2> : public S<I, I, I>, S<J, J, J> {};
       
       template <int I, int J, int K>
       void f(S<I, J, K>, S<I, I, I>);
       
       void g() {
         S<0, 0, 0> s0;
         S<0, 1, 2> s2;
       
         f(s0, s2);
       }

     Now, by the time we consider the unification involving `s2', we
     already know that we must have `f<0, 0, 0>'.  But, even though
     `S<0, 1, 2>' is derived from `S<0, 0, 0>', the code is not legal
     because there are two ways to unify base classes of S<0, 1, 2>
     with S<I, I, I>.  If we kept the already deduced knowledge, we
     would reject the possibility I=1.  */
  push_momentary ();
  copy_of_targs = make_temp_vec (TREE_VEC_LENGTH (targs));
  i = unify (tparms, copy_of_targs, CLASSTYPE_TI_ARGS (parm),
             CLASSTYPE_TI_ARGS (arg), UNIFY_ALLOW_NONE);
  pop_momentary ();
  
  /* If unification failed, we're done.  */
  if (i != 0)
    return NULL_TREE;
  else
    return arg;
}

/* Subroutine of get_template_base.  RVAL, if non-NULL, is a base we
   have alreay discovered to be satisfactory.  ARG_BINFO is the binfo
   for the base class of ARG that we are currently examining.  */

static tree
get_template_base_recursive (tparms, targs, parm,
                             arg_binfo, rval, flags)
     tree tparms;
     tree targs;
     tree arg_binfo;
     tree rval;
     tree parm;
     int flags;
{
  tree binfos;
  int i, n_baselinks;
  tree arg = BINFO_TYPE (arg_binfo);

  if (!(flags & GTB_IGNORE_TYPE))
    {
      tree r = try_class_unification (tparms, targs,
                                      parm, arg);

      /* If there is more than one satisfactory baseclass, then:

           [temp.deduct.call]

           If they yield more than one possible deduced A, the type
           deduction fails.

           applies.  */
      if (r && rval && !same_type_p (r, rval))
        return error_mark_node;
      else if (r)
        rval = r;
    }

  binfos = BINFO_BASETYPES (arg_binfo);
  n_baselinks = binfos ? TREE_VEC_LENGTH (binfos) : 0;

  /* Process base types.  */
  for (i = 0; i < n_baselinks; i++)
    {
      tree base_binfo = TREE_VEC_ELT (binfos, i);
      int this_virtual;

      /* Skip this base, if we've already seen it.  */
      if (BINFO_MARKED (base_binfo))
        continue;

      this_virtual = 
        (flags & GTB_VIA_VIRTUAL) || TREE_VIA_VIRTUAL (base_binfo);
      
      /* When searching for a non-virtual, we cannot mark virtually
         found binfos.  */
      if (! this_virtual)
        SET_BINFO_MARKED (base_binfo);
      
      rval = get_template_base_recursive (tparms, targs,
                                          parm,
                                          base_binfo, 
                                          rval,
                                          GTB_VIA_VIRTUAL * this_virtual);
      
      /* If we discovered more than one matching base class, we can
         stop now.  */
      if (rval == error_mark_node)
        return error_mark_node;
    }

  return rval;
}

/* Given a template type PARM and a class type ARG, find the unique
   base type in ARG that is an instance of PARM.  We do not examine
   ARG itself; only its base-classes.  If there is no appropriate base
   class, return NULL_TREE.  If there is more than one, return
   error_mark_node.  PARM may be the type of a partial specialization,
   as well as a plain template type.  Used by unify.  */

static tree
get_template_base (tparms, targs, parm, arg)
     tree tparms;
     tree targs;
     tree parm;
     tree arg;
{
  tree rval;
  tree arg_binfo;

  my_friendly_assert (IS_AGGR_TYPE_CODE (TREE_CODE (arg)), 92);
  
  arg_binfo = TYPE_BINFO (complete_type (arg));
  rval = get_template_base_recursive (tparms, targs,
                                      parm, arg_binfo, 
                                      NULL_TREE,
                                      GTB_IGNORE_TYPE);

  /* Since get_template_base_recursive marks the bases classes, we
     must unmark them here.  */
  dfs_walk (arg_binfo, dfs_unmark, markedp, 0);

  return rval;
}

/* Returns the level of DECL, which declares a template parameter.  */

static int
template_decl_level (decl)
     tree decl;
{
  switch (TREE_CODE (decl))
    {
    case TYPE_DECL:
    case TEMPLATE_DECL:
      return TEMPLATE_TYPE_LEVEL (TREE_TYPE (decl));

    case PARM_DECL:
      return TEMPLATE_PARM_LEVEL (DECL_INITIAL (decl));

    default:
      my_friendly_abort (0);
      return 0;
    }
}

/* Decide whether ARG can be unified with PARM, considering only the
   cv-qualifiers of each type, given STRICT as documented for unify.
   Returns non-zero iff the unification is OK on that basis.*/

static int
check_cv_quals_for_unify (strict, arg, parm)
     int strict;
     tree arg;
     tree parm;
{
  return !((!(strict & UNIFY_ALLOW_MORE_CV_QUAL)
            && !at_least_as_qualified_p (arg, parm))
           || (!(strict & UNIFY_ALLOW_LESS_CV_QUAL)
               && (!at_least_as_qualified_p (parm, arg))));
}

/* Takes parameters as for type_unification.  Returns 0 if the
   type deduction suceeds, 1 otherwise.  The parameter STRICT is a
   bitwise or of the following flags:

     UNIFY_ALLOW_NONE:
       Require an exact match between PARM and ARG.
     UNIFY_ALLOW_MORE_CV_QUAL:
       Allow the deduced ARG to be more cv-qualified than ARG.
     UNIFY_ALLOW_LESS_CV_QUAL:
       Allow the deduced ARG to be less cv-qualified than ARG.
     UNIFY_ALLOW_DERIVED:
       Allow the deduced ARG to be a template base class of ARG,
       or a pointer to a template base class of the type pointed to by
       ARG.
     UNIFY_ALLOW_INTEGER:
       Allow any integral type to be deduced.  See the TEMPLATE_PARM_INDEX
       case for more information.  */

static int
unify (tparms, targs, parm, arg, strict)
     tree tparms, targs, parm, arg;
     int strict;
{
  int idx;
  tree targ;
  tree tparm;

  /* I don't think this will do the right thing with respect to types.
     But the only case I've seen it in so far has been array bounds, where
     signedness is the only information lost, and I think that will be
     okay.  */
  while (TREE_CODE (parm) == NOP_EXPR)
    parm = TREE_OPERAND (parm, 0);

  if (arg == error_mark_node)
    return 1;
  if (arg == unknown_type_node)
    /* We can't deduce anything from this, but we might get all the
       template args from other function args.  */
    return 0;

  /* If PARM uses template parameters, then we can't bail out here,
     even if ARG == PARM, since we won't record unifications for the
     template parameters.  We might need them if we're trying to
     figure out which of two things is more specialized.  */
  if (arg == parm && !uses_template_parms (parm))
    return 0;

  /* Immediately reject some pairs that won't unify because of
     cv-qualification mismatches.  */
  if (TREE_CODE (arg) == TREE_CODE (parm)
      && TREE_CODE_CLASS (TREE_CODE (arg)) == 't'
      /* We check the cv-qualifiers when unifying with template type
         parameters below.  We want to allow ARG `const T' to unify with
         PARM `T' for example, when computing which of two templates
         is more specialized, for example.  */
      && TREE_CODE (arg) != TEMPLATE_TYPE_PARM
      && !check_cv_quals_for_unify (strict, arg, parm))
    return 1;

  switch (TREE_CODE (parm))
    {
    case TYPENAME_TYPE:
      /* In a type which contains a nested-name-specifier, template
         argument values cannot be deduced for template parameters used
         within the nested-name-specifier.  */
      return 0;

    case TEMPLATE_TYPE_PARM:
    case TEMPLATE_TEMPLATE_PARM:
      tparm = TREE_VALUE (TREE_VEC_ELT (tparms, 0));

      if (TEMPLATE_TYPE_LEVEL (parm)
          != template_decl_level (tparm))
        /* The PARM is not one we're trying to unify.  Just check
           to see if it matches ARG.  */
        return (TREE_CODE (arg) == TREE_CODE (parm)
                && same_type_p (parm, arg)) ? 0 : 1;
      idx = TEMPLATE_TYPE_IDX (parm);
      targ = TREE_VEC_ELT (targs, idx);
      tparm = TREE_VALUE (TREE_VEC_ELT (tparms, idx));

      /* Check for mixed types and values.  */
      if ((TREE_CODE (parm) == TEMPLATE_TYPE_PARM
           && TREE_CODE (tparm) != TYPE_DECL)
          || (TREE_CODE (parm) == TEMPLATE_TEMPLATE_PARM 
              && TREE_CODE (tparm) != TEMPLATE_DECL))
        return 1;

      if (TREE_CODE (parm) == TEMPLATE_TEMPLATE_PARM)
        {
          if (TEMPLATE_TEMPLATE_PARM_TEMPLATE_INFO (parm))
            {
              /* We arrive here when PARM does not involve template 
                 specialization.  */

              /* ARG must be constructed from a template class.  */
              if (TREE_CODE (arg) != RECORD_TYPE || !CLASSTYPE_TEMPLATE_INFO (arg))
                return 1;

              {
                tree parmtmpl = TYPE_TI_TEMPLATE (parm);
                tree parmvec = TYPE_TI_ARGS (parm);
                tree argvec = CLASSTYPE_TI_ARGS (arg);
                tree argtmplvec
                  = DECL_INNERMOST_TEMPLATE_PARMS (CLASSTYPE_TI_TEMPLATE (arg));
                int i;

                /* The parameter and argument roles have to be switched here 
                   in order to handle default arguments properly.  For example, 
                   template<template <class> class TT> void f(TT<int>) 
                   should be able to accept vector<int> which comes from 
                   template <class T, class Allocator = allocator> 
                   class vector.  */

                if (coerce_template_parms (argtmplvec, parmvec, parmtmpl, 0, 1)
                    == error_mark_node)
                  return 1;
          
                /* Deduce arguments T, i from TT<T> or TT<i>.  
                   We check each element of PARMVEC and ARGVEC individually
                   rather than the whole TREE_VEC since they can have
                   different number of elements.  */

                for (i = 0; i < TREE_VEC_LENGTH (parmvec); ++i)
                  {
                    tree t = TREE_VEC_ELT (parmvec, i);

                    if (unify (tparms, targs, t, 
                               TREE_VEC_ELT (argvec, i), 
                               UNIFY_ALLOW_NONE))
                      return 1;
                  }
              }
              arg = CLASSTYPE_TI_TEMPLATE (arg);
            }
        }
      else
        {
          /* If PARM is `const T' and ARG is only `int', we don't have
             a match unless we are allowing additional qualification.
             If ARG is `const int' and PARM is just `T' that's OK;
             that binds `const int' to `T'.  */
          if (!check_cv_quals_for_unify (strict | UNIFY_ALLOW_LESS_CV_QUAL, 
                                         arg, parm))
            return 1;

          /* Consider the case where ARG is `const volatile int' and
             PARM is `const T'.  Then, T should be `volatile int'.  */
          arg = 
            cp_build_qualified_type (arg,
                                     CP_TYPE_QUALS (arg) 
                                     & ~CP_TYPE_QUALS (parm));
        }

      /* Simple cases: Value already set, does match or doesn't.  */
      if (targ != NULL_TREE && same_type_p (targ, arg))
        return 0;
      else if (targ)
        return 1;

      /* Make sure that ARG is not a variable-sized array.  (Note that
         were talking about variable-sized arrays (like `int[n]'),
         rather than arrays of unknown size (like `int[]').)  We'll
         get very confused by such a type since the bound of the array
         will not be computable in an instantiation.  Besides, such
         types are not allowed in ISO C++, so we can do as we please
         here.  */
      if (TREE_CODE (arg) == ARRAY_TYPE 
          && !uses_template_parms (arg)
          && (TREE_CODE (TYPE_MAX_VALUE (TYPE_DOMAIN (arg)))
              != INTEGER_CST))
        return 1;

      TREE_VEC_ELT (targs, idx) = arg;
      return 0;

    case TEMPLATE_PARM_INDEX:
      tparm = TREE_VALUE (TREE_VEC_ELT (tparms, 0));

      if (TEMPLATE_PARM_LEVEL (parm) 
          != template_decl_level (tparm))
        /* The PARM is not one we're trying to unify.  Just check
           to see if it matches ARG.  */
        return (TREE_CODE (arg) == TREE_CODE (parm)
                && cp_tree_equal (parm, arg) > 0) ? 0 : 1;

      idx = TEMPLATE_PARM_IDX (parm);
      targ = TREE_VEC_ELT (targs, idx);

      if (targ)
        {
          int i = (cp_tree_equal (targ, arg) > 0);
          if (i == 1)
            return 0;
          else if (i == 0)
            return 1;
          else
            my_friendly_abort (42);
        }

      /* [temp.deduct.type] If, in the declaration of a function template
         with a non-type template-parameter, the non-type
         template-parameter is used in an expression in the function
         parameter-list and, if the corresponding template-argument is
         deduced, the template-argument type shall match the type of the
         template-parameter exactly, except that a template-argument
         deduced from an array bound may be of any integral type.  */
      if (same_type_p (TREE_TYPE (arg), TREE_TYPE (parm)))
        /* OK */;
      else if ((strict & UNIFY_ALLOW_INTEGER)
               && (TREE_CODE (TREE_TYPE (parm)) == INTEGER_TYPE
                   || TREE_CODE (TREE_TYPE (parm)) == BOOLEAN_TYPE))
        /* OK */;
      else
        return 1;

      TREE_VEC_ELT (targs, idx) = copy_to_permanent (arg);
      return 0;

    case POINTER_TYPE:
      {
        int sub_strict;

        if (TREE_CODE (arg) == RECORD_TYPE && TYPE_PTRMEMFUNC_FLAG (arg))
          return (unify (tparms, targs, parm, 
                         TYPE_PTRMEMFUNC_FN_TYPE (arg), strict));
        
        if (TREE_CODE (arg) != POINTER_TYPE)
          return 1;
        
        /* [temp.deduct.call]

           A can be another pointer or pointer to member type that can
           be converted to the deduced A via a qualification
           conversion (_conv.qual_).

           We pass down STRICT here rather than UNIFY_ALLOW_NONE.
           This will allow for additional cv-qualification of the
           pointed-to types if appropriate.  In general, this is a bit
           too generous; we are only supposed to allow qualification
           conversions and this method will allow an ARG of char** and
           a deduced ARG of const char**.  However, overload
           resolution will subsequently invalidate the candidate, so
           this is probably OK.  */
        sub_strict = strict;
        
        if (TREE_CODE (TREE_TYPE (arg)) != RECORD_TYPE
            || TYPE_PTRMEMFUNC_FLAG (TREE_TYPE (arg)))
          /* The derived-to-base conversion only persists through one
             level of pointers.  */
          sub_strict &= ~UNIFY_ALLOW_DERIVED;

        return unify (tparms, targs, TREE_TYPE (parm), TREE_TYPE
                      (arg), sub_strict);
      }

    case REFERENCE_TYPE:
      if (TREE_CODE (arg) != REFERENCE_TYPE)
        return 1;
      return unify (tparms, targs, TREE_TYPE (parm), TREE_TYPE (arg),
                    UNIFY_ALLOW_NONE);

    case ARRAY_TYPE:
      if (TREE_CODE (arg) != ARRAY_TYPE)
        return 1;
      if ((TYPE_DOMAIN (parm) == NULL_TREE)
          != (TYPE_DOMAIN (arg) == NULL_TREE))
        return 1;
      if (TYPE_DOMAIN (parm) != NULL_TREE
          && unify (tparms, targs, TYPE_DOMAIN (parm),
                    TYPE_DOMAIN (arg), UNIFY_ALLOW_NONE) != 0)
        return 1;
      return unify (tparms, targs, TREE_TYPE (parm), TREE_TYPE (arg),
                    UNIFY_ALLOW_NONE);

    case REAL_TYPE:
    case COMPLEX_TYPE:
    case INTEGER_TYPE:
    case BOOLEAN_TYPE:
    case VOID_TYPE:
      if (TREE_CODE (arg) != TREE_CODE (parm))
        return 1;

      if (TREE_CODE (parm) == INTEGER_TYPE
          && TREE_CODE (TYPE_MAX_VALUE (parm)) != INTEGER_CST)
        {
          if (TYPE_MIN_VALUE (parm) && TYPE_MIN_VALUE (arg)
              && unify (tparms, targs, TYPE_MIN_VALUE (parm),
                        TYPE_MIN_VALUE (arg), UNIFY_ALLOW_INTEGER))
            return 1;
          if (TYPE_MAX_VALUE (parm) && TYPE_MAX_VALUE (arg)
              && unify (tparms, targs, TYPE_MAX_VALUE (parm),
                        TYPE_MAX_VALUE (arg), UNIFY_ALLOW_INTEGER))
            return 1;
        }
      /* We use the TYPE_MAIN_VARIANT since we have already
         checked cv-qualification at the top of the
         function.  */
      else if (!same_type_p (TYPE_MAIN_VARIANT (arg),
                             TYPE_MAIN_VARIANT (parm)))
        return 1;

      /* As far as unification is concerned, this wins.  Later checks
         will invalidate it if necessary.  */
      return 0;

      /* Types INTEGER_CST and MINUS_EXPR can come from array bounds.  */
      /* Type INTEGER_CST can come from ordinary constant template args.  */
    case INTEGER_CST:
      while (TREE_CODE (arg) == NOP_EXPR)
        arg = TREE_OPERAND (arg, 0);

      if (TREE_CODE (arg) != INTEGER_CST)
        return 1;
      return !tree_int_cst_equal (parm, arg);

    case TREE_VEC:
      {
        int i;
        if (TREE_CODE (arg) != TREE_VEC)
          return 1;
        if (TREE_VEC_LENGTH (parm) != TREE_VEC_LENGTH (arg))
          return 1;
        for (i = TREE_VEC_LENGTH (parm) - 1; i >= 0; i--)
          if (unify (tparms, targs,
                     TREE_VEC_ELT (parm, i), TREE_VEC_ELT (arg, i),
                     UNIFY_ALLOW_NONE))
            return 1;
        return 0;
      }

    case RECORD_TYPE:
    case UNION_TYPE:
      if (TYPE_PTRMEMFUNC_FLAG (parm))
        return unify (tparms, targs, TYPE_PTRMEMFUNC_FN_TYPE (parm),
                      arg, strict);

      if (TREE_CODE (arg) != TREE_CODE (parm))
        return 1;
  
      if (CLASSTYPE_TEMPLATE_INFO (parm))
        {
          tree t = NULL_TREE;

          if (strict & UNIFY_ALLOW_DERIVED)
            {
              /* First, we try to unify the PARM and ARG directly.  */
              t = try_class_unification (tparms, targs,
                                         parm, arg);

              if (!t)
                {
                  /* Fallback to the special case allowed in
                     [temp.deduct.call]:
                     
                       If P is a class, and P has the form
                       template-id, then A can be a derived class of
                       the deduced A.  Likewise, if P is a pointer to
                       a class of the form template-id, A can be a
                       pointer to a derived class pointed to by the
                       deduced A.  */
                  t = get_template_base (tparms, targs,
                                         parm, arg);

                  if (! t || t == error_mark_node)
                    return 1;
                }
            }
          else if (CLASSTYPE_TEMPLATE_INFO (arg) 
                   && (CLASSTYPE_TI_TEMPLATE (parm) 
                       == CLASSTYPE_TI_TEMPLATE (arg)))
            /* Perhaps PARM is something like S<U> and ARG is S<int>.
               Then, we should unify `int' and `U'.  */
            t = arg;
          else
            /* There's no chance of unication succeeding.  */
            return 1;

          return unify (tparms, targs, CLASSTYPE_TI_ARGS (parm),
                        CLASSTYPE_TI_ARGS (t), UNIFY_ALLOW_NONE);
        }
      else if (!same_type_p (TYPE_MAIN_VARIANT (parm),
                             TYPE_MAIN_VARIANT (arg)))
        return 1;
      return 0;

    case METHOD_TYPE:
    case FUNCTION_TYPE:
      if (TREE_CODE (arg) != TREE_CODE (parm))
        return 1;

      if (unify (tparms, targs, TREE_TYPE (parm),
                 TREE_TYPE (arg), UNIFY_ALLOW_NONE))
        return 1;
      return type_unification_real (tparms, targs, TYPE_ARG_TYPES (parm),
                                    TYPE_ARG_TYPES (arg), 1, 
                                    DEDUCE_EXACT, 0);

    case OFFSET_TYPE:
      if (TREE_CODE (arg) != OFFSET_TYPE)
        return 1;
      if (unify (tparms, targs, TYPE_OFFSET_BASETYPE (parm),
                 TYPE_OFFSET_BASETYPE (arg), UNIFY_ALLOW_NONE))
        return 1;
      return unify (tparms, targs, TREE_TYPE (parm), TREE_TYPE (arg),
                    strict);

    case CONST_DECL:
      if (arg != decl_constant_value (parm)) 
        return 1;
      return 0;

    case TEMPLATE_DECL:
      /* Matched cases are handled by the ARG == PARM test above.  */
      return 1;

    case MINUS_EXPR:
      if (TREE_CODE (TREE_OPERAND (parm, 1)) == INTEGER_CST)
        {
          /* We handle this case specially, since it comes up with
             arrays.  In particular, something like:

             template <int N> void f(int (&x)[N]);

             Here, we are trying to unify the range type, which
             looks like [0 ... (N - 1)].  */
          tree t, t1, t2;
          t1 = TREE_OPERAND (parm, 0);
          t2 = TREE_OPERAND (parm, 1);

          /* Should this be a regular fold?  */
          t = maybe_fold_nontype_arg (build (PLUS_EXPR,
                                             integer_type_node,
                                             arg, t2));

          return unify (tparms, targs, t1, t, strict);
        }
      /* else fall through */

    default:
      if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (TREE_CODE (parm))))
        /* We're looking at an expression.  This can happen with
           something like: 
           
             template <int I>
             void foo(S<I>, S<I + 2>);

           This is a "nondeduced context":

             [deduct.type]
           
             The nondeduced contexts are:

             --A type that is a template-id in which one or more of
               the template-arguments is an expression that references
               a template-parameter.  

           In these cases, we assume deduction succeeded, but don't
           actually infer any unifications.  */
        return 0;
      else
        sorry ("use of `%s' in template type unification",
               tree_code_name [(int) TREE_CODE (parm)]);

      return 1;
    }
}
\f
/* Called if RESULT is explicitly instantiated, or is a member of an
   explicitly instantiated class, or if using -frepo and the
   instantiation of RESULT has been assigned to this file.  */

void
mark_decl_instantiated (result, extern_p)
     tree result;
     int extern_p;
{
  if (TREE_CODE (result) != FUNCTION_DECL)
    /* The TREE_PUBLIC flag for function declarations will have been
       set correctly by tsubst.  */
    TREE_PUBLIC (result) = 1;

  if (! extern_p)
    {
      DECL_INTERFACE_KNOWN (result) = 1;
      DECL_NOT_REALLY_EXTERN (result) = 1;

      /* Always make artificials weak.  */
      if (DECL_ARTIFICIAL (result) && flag_weak)
        comdat_linkage (result);
      /* For WIN32 we also want to put explicit instantiations in
         linkonce sections.  */
      else if (TREE_PUBLIC (result))
        maybe_make_one_only (result);
    }
  else if (TREE_CODE (result) == FUNCTION_DECL)
    mark_inline_for_output (result);
}

/* Given two function templates PAT1 and PAT2, and explicit template
   arguments EXPLICIT_ARGS return:

   1 if PAT1 is more specialized than PAT2 as described in [temp.func.order].
   -1 if PAT2 is more specialized than PAT1.
   0 if neither is more specialized.  */
   
int
more_specialized (pat1, pat2, explicit_args)
     tree pat1, pat2, explicit_args;
{
  tree targs;
  int winner = 0;

  targs = get_bindings_overload (pat1, DECL_RESULT (pat2), explicit_args);
  if (targs)
    --winner;

  targs = get_bindings_overload (pat2, DECL_RESULT (pat1), explicit_args);
  if (targs)
    ++winner;

  return winner;
}

/* Given two class template specialization list nodes PAT1 and PAT2, return:

   1 if PAT1 is more specialized than PAT2 as described in [temp.class.order].
   -1 if PAT2 is more specialized than PAT1.
   0 if neither is more specialized.  */
   
int
more_specialized_class (pat1, pat2)
     tree pat1, pat2;
{
  tree targs;
  int winner = 0;

  targs = get_class_bindings (TREE_VALUE (pat1), TREE_PURPOSE (pat1),
                              TREE_PURPOSE (pat2));
  if (targs)
    --winner;

  targs = get_class_bindings (TREE_VALUE (pat2), TREE_PURPOSE (pat2),
                              TREE_PURPOSE (pat1));
  if (targs)
    ++winner;

  return winner;
}

/* Return the template arguments that will produce the function signature
   DECL from the function template FN, with the explicit template
   arguments EXPLICIT_ARGS.  If CHECK_RETTYPE is 1, the return type must
   also match.  Return NULL_TREE if no satisfactory arguments could be
   found.  */

static tree
get_bindings_real (fn, decl, explicit_args, check_rettype)
     tree fn, decl, explicit_args;
     int check_rettype;
{
  int ntparms = DECL_NTPARMS (fn);
  tree targs = make_scratch_vec (ntparms);
  tree decl_type;
  tree decl_arg_types;
  int i;

  /* Substitute the explicit template arguments into the type of DECL.
     The call to fn_type_unification will handle substitution into the
     FN.  */
  decl_type = TREE_TYPE (decl);
  if (explicit_args && uses_template_parms (decl_type))
    {
      tree tmpl;
      tree converted_args;

      if (DECL_TEMPLATE_INFO (decl))
        tmpl = DECL_TI_TEMPLATE (decl);
      else
        /* We can get here for some illegal specializations.  */
        return NULL_TREE;

      converted_args
        = (coerce_template_parms (DECL_INNERMOST_TEMPLATE_PARMS (tmpl),
                                  explicit_args, NULL_TREE,
                                  /*complain=*/0, 
                                  /*require_all_arguments=*/0));
      if (converted_args == error_mark_node)
        return NULL_TREE;
      
      decl_type = tsubst (decl_type, converted_args, /*complain=*/0, 
                          NULL_TREE); 
      if (decl_type == error_mark_node)
        return NULL_TREE;
    }

  /* If FN is a static member function, adjust the type of DECL
     appropriately.  */
  decl_arg_types = TYPE_ARG_TYPES (decl_type);
  if (DECL_STATIC_FUNCTION_P (fn) 
      && DECL_NONSTATIC_MEMBER_FUNCTION_P (decl))
    decl_arg_types = TREE_CHAIN (decl_arg_types);

  i = fn_type_unification (fn, explicit_args, targs, 
                           decl_arg_types,
                           TREE_TYPE (decl_type),
                           DEDUCE_EXACT);

  if (i != 0)
    return NULL_TREE;

  if (check_rettype)
    {
      /* Check to see that the resulting return type is also OK.  */
      tree t = tsubst (TREE_TYPE (TREE_TYPE (fn)), targs,
                       /*complain=*/0, NULL_TREE);

      if (!same_type_p (t, TREE_TYPE (TREE_TYPE (decl))))
        return NULL_TREE;
    }

  return targs;
}

/* For most uses, we want to check the return type.  */

tree 
get_bindings (fn, decl, explicit_args)
     tree fn, decl, explicit_args;
{
  return get_bindings_real (fn, decl, explicit_args, 1);
}

/* But for more_specialized, we only care about the parameter types.  */

static tree
get_bindings_overload (fn, decl, explicit_args)
     tree fn, decl, explicit_args;
{
  return get_bindings_real (fn, decl, explicit_args, 0);
}

/* Return the innermost template arguments that, when applied to a
   template specialization whose innermost template parameters are
   TPARMS, and whose specialization arguments are ARGS, yield the
   ARGS.  

   For example, suppose we have:

     template <class T, class U> struct S {};
     template <class T> struct S<T*, int> {};

   Then, suppose we want to get `S<double*, int>'.  The TPARMS will be
   {T}, the PARMS will be {T*, int} and the ARGS will be {double*,
   int}.  The resulting vector will be {double}, indicating that `T'
   is bound to `double'.  */

static tree
get_class_bindings (tparms, parms, args)
     tree tparms, parms, args;
{
  int i, ntparms = TREE_VEC_LENGTH (tparms);
  tree vec = make_temp_vec (ntparms);

  args = innermost_args (args);

  if (unify (tparms, vec, parms, args, UNIFY_ALLOW_NONE))
    return NULL_TREE;

  for (i =  0; i < ntparms; ++i)
    if (! TREE_VEC_ELT (vec, i))
      return NULL_TREE;

  return vec;
}

/* In INSTANTIATIONS is a list of <INSTANTIATION, TEMPLATE> pairs.
   Pick the most specialized template, and return the corresponding
   instantiation, or if there is no corresponding instantiation, the
   template itself.  EXPLICIT_ARGS is any template arguments explicity
   mentioned in a template-id.  If there is no most specialized
   tempalte, error_mark_node is returned.  If there are no templates
   at all, NULL_TREE is returned.  */

tree
most_specialized_instantiation (instantiations, explicit_args)
     tree instantiations;
     tree explicit_args;
{
  tree fn, champ;
  int fate;

  if (!instantiations)
    return NULL_TREE;

  champ = instantiations;
  for (fn = TREE_CHAIN (instantiations); fn; fn = TREE_CHAIN (fn))
    {
      fate = more_specialized (TREE_VALUE (champ), 
                               TREE_VALUE (fn), explicit_args);
      if (fate == 1)
        ;
      else
        {
          if (fate == 0)
            {
              fn = TREE_CHAIN (fn);
              if (! fn)
                return error_mark_node;
            }
          champ = fn;
        }
    }

  for (fn = instantiations; fn && fn != champ; fn = TREE_CHAIN (fn))
    {
      fate = more_specialized (TREE_VALUE (champ), 
                               TREE_VALUE (fn), explicit_args);
      if (fate != 1)
        return error_mark_node;
    }

  return TREE_PURPOSE (champ) ? TREE_PURPOSE (champ) : TREE_VALUE (champ);
}

/* Return the most specialized of the list of templates in FNS that can
   produce an instantiation matching DECL, given the explicit template
   arguments EXPLICIT_ARGS.  */

static tree
most_specialized (fns, decl, explicit_args)
     tree fns, decl, explicit_args;
{
  tree candidates = NULL_TREE;
  tree fn, args;

  for (fn = fns; fn; fn = TREE_CHAIN (fn))
    {
      tree candidate = TREE_VALUE (fn);

      args = get_bindings (candidate, decl, explicit_args);
      if (args)
        candidates = scratch_tree_cons (NULL_TREE, candidate, 
                                        candidates);
    }

  return most_specialized_instantiation (candidates, explicit_args);
}

/* If DECL is a specialization of some template, return the most
   general such template.  For example, given:

     template <class T> struct S { template <class U> void f(U); };

   if TMPL is `template <class U> void S<int>::f(U)' this will return
   the full template.  This function will not trace past partial
   specializations, however.  For example, given in addition:

     template <class T> struct S<T*> { template <class U> void f(U); };

   if TMPL is `template <class U> void S<int*>::f(U)' this will return
   `template <class T> template <class U> S<T*>::f(U)'.  */

static tree
most_general_template (decl)
     tree decl;
{
  while (DECL_TEMPLATE_INFO (decl))
    decl = DECL_TI_TEMPLATE (decl);

  return decl;
}

/* Return the most specialized of the class template specializations
   of TMPL which can produce an instantiation matching ARGS, or
   error_mark_node if the choice is ambiguous.  */

static tree
most_specialized_class (tmpl, args)
     tree tmpl;
     tree args;
{
  tree list = NULL_TREE;
  tree t;
  tree champ;
  int fate;

  tmpl = most_general_template (tmpl);
  for (t = DECL_TEMPLATE_SPECIALIZATIONS (tmpl); t; t = TREE_CHAIN (t))
    {
      tree spec_args 
        = get_class_bindings (TREE_VALUE (t), TREE_PURPOSE (t), args);
      if (spec_args)
        {
          list = decl_tree_cons (TREE_PURPOSE (t), TREE_VALUE (t), list);
          TREE_TYPE (list) = TREE_TYPE (t);
        }
    }

  if (! list)
    return NULL_TREE;

  t = list;
  champ = t;
  t = TREE_CHAIN (t);
  for (; t; t = TREE_CHAIN (t))
    {
      fate = more_specialized_class (champ, t);
      if (fate == 1)
        ;
      else
        {
          if (fate == 0)
            {
              t = TREE_CHAIN (t);
              if (! t)
                return error_mark_node;
            }
          champ = t;
        }
    }

  for (t = list; t && t != champ; t = TREE_CHAIN (t))
    {
      fate = more_specialized_class (champ, t);
      if (fate != 1)
        return error_mark_node;
    }

  return champ;
}

/* called from the parser.  */

void
do_decl_instantiation (declspecs, declarator, storage)
     tree declspecs, declarator, storage;
{
  tree decl = grokdeclarator (declarator, declspecs, NORMAL, 0, NULL_TREE);
  tree result = NULL_TREE;
  int extern_p = 0;

  if (! DECL_LANG_SPECIFIC (decl))
    {
      cp_error ("explicit instantiation of non-template `%#D'", decl);
      return;
    }
  else if (TREE_CODE (decl) == VAR_DECL)
    {
      /* There is an asymmetry here in the way VAR_DECLs and
         FUNCTION_DECLs are handled by grokdeclarator.  In the case of
         the latter, the DECL we get back will be marked as a
         template instantiation, and the appropriate
         DECL_TEMPLATE_INFO will be set up.  This does not happen for
         VAR_DECLs so we do the lookup here.  Probably, grokdeclarator
         should handle VAR_DECLs as it currently handles
         FUNCTION_DECLs.  */
      result = lookup_field (DECL_CONTEXT (decl), DECL_NAME (decl), 0, 0);
      if (result && TREE_CODE (result) != VAR_DECL)
        {
          cp_error ("no matching template for `%D' found", result);
          return;
        }
    }
  else if (TREE_CODE (decl) != FUNCTION_DECL)
    {
      cp_error ("explicit instantiation of `%#D'", decl);
      return;
    }
  else
    result = decl;

  /* Check for various error cases.  Note that if the explicit
     instantiation is legal the RESULT will currently be marked as an
     *implicit* instantiation; DECL_EXPLICIT_INSTANTIATION is not set
     until we get here.  */

  if (DECL_TEMPLATE_SPECIALIZATION (result))
    {
      /* [temp.spec]

         No program shall both explicitly instantiate and explicitly
         specialize a template.  */
      cp_error ("explicit instantiation of `%#D' after", result);
      cp_error_at ("explicit specialization here", result);
      return;
    }
  else if (DECL_EXPLICIT_INSTANTIATION (result))
    {
      /* [temp.spec]

         No program shall explicitly instantiate any template more
         than once.  

         We check DECL_INTERFACE_KNOWN so as not to complain when the
         first instantiation was `extern' and the second is not, and
         EXTERN_P for the opposite case.  */
      if (DECL_INTERFACE_KNOWN (result) && !extern_p)
        cp_error ("duplicate explicit instantiation of `%#D'", result);

      /* If we've already instantiated the template, just return now.  */
      if (DECL_INTERFACE_KNOWN (result))
        return;
    }
  else if (!DECL_IMPLICIT_INSTANTIATION (result))
    {
      cp_error ("no matching template for `%D' found", result);
      return;
    }
  else if (!DECL_TEMPLATE_INFO (result))
    {
      cp_pedwarn ("explicit instantiation of non-template `%#D'", result);
      return;
    }

  if (flag_external_templates)
    return;

  if (storage == NULL_TREE)
    ;
  else if (storage == ridpointers[(int) RID_EXTERN])
    {
      if (pedantic)
        cp_pedwarn ("ANSI C++ forbids the use of `extern' on explicit instantiations");
      extern_p = 1;
    }
  else
    cp_error ("storage class `%D' applied to template instantiation",
              storage);

  SET_DECL_EXPLICIT_INSTANTIATION (result);
  mark_decl_instantiated (result, extern_p);
  repo_template_instantiated (result, extern_p);
  if (! extern_p)
    instantiate_decl (result);
}

void
mark_class_instantiated (t, extern_p)
     tree t;
     int extern_p;
{
  SET_CLASSTYPE_EXPLICIT_INSTANTIATION (t);
  SET_CLASSTYPE_INTERFACE_KNOWN (t);
  CLASSTYPE_INTERFACE_ONLY (t) = extern_p;
  CLASSTYPE_VTABLE_NEEDS_WRITING (t) = ! extern_p;
  TYPE_DECL_SUPPRESS_DEBUG (TYPE_NAME (t)) = extern_p;
  if (! extern_p)
    {
      CLASSTYPE_DEBUG_REQUESTED (t) = 1;
      rest_of_type_compilation (t, 1);
    }
}     

void
do_type_instantiation (t, storage)
     tree t, storage;
{
  int extern_p = 0;
  int nomem_p = 0;
  int static_p = 0;

  if (TREE_CODE (t) == TYPE_DECL)
    t = TREE_TYPE (t);

  if (! CLASS_TYPE_P (t) || ! CLASSTYPE_TEMPLATE_INFO (t))
    {
      cp_error ("explicit instantiation of non-template type `%T'", t);
      return;
    }

  complete_type (t);

  /* With -fexternal-templates, explicit instantiations are treated the same
     as implicit ones.  */
  if (flag_external_templates)
    return;

  if (TYPE_SIZE (t) == NULL_TREE)
    {
      cp_error ("explicit instantiation of `%#T' before definition of template",
                t);
      return;
    }

  if (storage != NULL_TREE)
    {
      if (pedantic)
        cp_pedwarn("ANSI C++ forbids the use of `%s' on explicit instantiations", 
                   IDENTIFIER_POINTER (storage));

      if (storage == ridpointers[(int) RID_INLINE])
        nomem_p = 1;
      else if (storage == ridpointers[(int) RID_EXTERN])
        extern_p = 1;
      else if (storage == ridpointers[(int) RID_STATIC])
        static_p = 1;
      else
        {
          cp_error ("storage class `%D' applied to template instantiation",
                    storage);
          extern_p = 0;
        }
    }

  if (CLASSTYPE_TEMPLATE_SPECIALIZATION (t))
    {
      /* [temp.spec]

         No program shall both explicitly instantiate and explicitly
         specialize a template.  */
      cp_error ("explicit instantiation of `%#T' after", t);
      cp_error_at ("explicit specialization here", t);
      return;
    }
  else if (CLASSTYPE_EXPLICIT_INSTANTIATION (t))
    {
      /* [temp.spec]

         No program shall explicitly instantiate any template more
         than once.  

         If CLASSTYPE_INTERFACE_ONLY, then the first explicit
         instantiation was `extern', and if EXTERN_P then the second
         is.  Both cases are OK.  */
      if (!CLASSTYPE_INTERFACE_ONLY (t) && !extern_p)
        cp_error ("duplicate explicit instantiation of `%#T'", t);
      
      /* If we've already instantiated the template, just return now.  */
      if (!CLASSTYPE_INTERFACE_ONLY (t))
        return;
    }

  mark_class_instantiated (t, extern_p);
  repo_template_instantiated (t, extern_p);

  if (nomem_p)
    return;

  {
    tree tmp;

    /* In contrast to implicit instantiation, where only the
       declarations, and not the definitions, of members are
       instantiated, we have here:

         [temp.explicit]

         The explicit instantiation of a class template specialization
         implies the instantiation of all of its members not
         previously explicitly specialized in the translation unit
         containing the explicit instantiation.  

       Of course, we can't instantiate member template classes, since
       we don't have any arguments for them.  Note that the standard
       is unclear on whether the instatiation of the members are
       *explicit* instantiations or not.  We choose to be generous,
       and not set DECL_EXPLICIT_INSTANTIATION.  Therefore, we allow
       the explicit instantiation of a class where some of the members
       have no definition in the current translation unit.  */

    if (! static_p)
      for (tmp = TYPE_METHODS (t); tmp; tmp = TREE_CHAIN (tmp))
        if (TREE_CODE (tmp) == FUNCTION_DECL
            && DECL_TEMPLATE_INSTANTIATION (tmp))
          {
            mark_decl_instantiated (tmp, extern_p);
            repo_template_instantiated (tmp, extern_p);
            if (! extern_p)
              instantiate_decl (tmp);
          }

    for (tmp = TYPE_FIELDS (t); tmp; tmp = TREE_CHAIN (tmp))
      if (TREE_CODE (tmp) == VAR_DECL && DECL_TEMPLATE_INSTANTIATION (tmp))
        {
          mark_decl_instantiated (tmp, extern_p);
          repo_template_instantiated (tmp, extern_p);
          if (! extern_p)
            instantiate_decl (tmp);
        }

    for (tmp = CLASSTYPE_TAGS (t); tmp; tmp = TREE_CHAIN (tmp))
      if (IS_AGGR_TYPE (TREE_VALUE (tmp))
          && !uses_template_parms (CLASSTYPE_TI_ARGS (TREE_VALUE (tmp))))
        do_type_instantiation (TYPE_MAIN_DECL (TREE_VALUE (tmp)), storage);
  }
}

/* Given a function DECL, which is a specialization of TMPL, modify
   DECL to be a re-instantiation of TMPL with the same template
   arguments.  TMPL should be the template into which tsubst'ing
   should occur for DECL, not the most general template.

   One reason for doing this is a scenario like this:

     template <class T>
     void f(const T&, int i);

     void g() { f(3, 7); }

     template <class T>
     void f(const T& t, const int i) { }

   Note that when the template is first instantiated, with
   instantiate_template, the resulting DECL will have no name for the
   first parameter, and the wrong type for the second.  So, when we go
   to instantiate the DECL, we regenerate it.  */

static void
regenerate_decl_from_template (decl, tmpl)
     tree decl;
     tree tmpl;
{
  tree args;
  tree code_pattern;
  tree new_decl;
  tree gen_tmpl;
  int unregistered;

  args = DECL_TI_ARGS (decl);
  code_pattern = DECL_TEMPLATE_RESULT (tmpl);

  /* Unregister the specialization so that when we tsubst we will not
     just return DECL.  We don't have to unregister DECL from TMPL
     because if would only be registered there if it were a partial
     instantiation of a specialization, which it isn't: it's a full
     instantiation.  */
  gen_tmpl = most_general_template (tmpl);
  unregistered = unregister_specialization (decl, gen_tmpl);

  /* If the DECL was not unregistered then something peculiar is
     happening: we created a specialization but did not call
     register_specialization for it.  */
  my_friendly_assert (unregistered, 0);

  if (TREE_CODE (decl) == VAR_DECL)
    /* Make sure that we can see identifiers, and compute access
       correctly, for the class members used in the declaration of
       this static variable.  */
    pushclass (DECL_CONTEXT (decl), 2);

  /* Do the substitution to get the new declaration.  */
  new_decl = tsubst (code_pattern, args, /*complain=*/1, NULL_TREE);

  if (TREE_CODE (decl) == VAR_DECL)
    {
      /* Set up DECL_INITIAL, since tsubst doesn't.  */
      DECL_INITIAL (new_decl) = 
        tsubst_expr (DECL_INITIAL (code_pattern), args, 
                     /*complain=*/1, DECL_TI_TEMPLATE (decl));
      /* Pop the class context we pushed above.  */
      popclass (1);
    }
  else if (TREE_CODE (decl) == FUNCTION_DECL)
    {
      /* Convince duplicate_decls to use the DECL_ARGUMENTS from the
         new decl.  */ 
      DECL_INITIAL (new_decl) = error_mark_node;
      /* And don't complain about a duplicate definition.  */
      DECL_INITIAL (decl) = NULL_TREE;
    }

  /* The immediate parent of the new template is still whatever it was
     before, even though tsubst sets DECL_TI_TEMPLATE up as the most
     general template.  We also reset the DECL_ASSEMBLER_NAME since
     tsubst always calculates the name as if the function in question
     were really a template instance, and sometimes, with friend
     functions, this is not so.  See tsubst_friend_function for
     details.  */
  DECL_TI_TEMPLATE (new_decl) = DECL_TI_TEMPLATE (decl);
  DECL_ASSEMBLER_NAME (new_decl) = DECL_ASSEMBLER_NAME (decl);
  DECL_RTL (new_decl) = DECL_RTL (decl);

  /* Call duplicate decls to merge the old and new declarations.  */
  duplicate_decls (new_decl, decl);

  /* Now, re-register the specialization.  */
  register_specialization (decl, gen_tmpl, args);
}

/* Produce the definition of D, a _DECL generated from a template.  */

tree
instantiate_decl (d)
     tree d;
{
  tree tmpl = DECL_TI_TEMPLATE (d);
  tree args = DECL_TI_ARGS (d);
  tree td;
  tree code_pattern;
  tree spec;
  tree gen_tmpl;
  int nested = in_function_p ();
  int pattern_defined;
  int line = lineno;
  char *file = input_filename;

  /* This function should only be used to instantiate templates for
     functions and static member variables.  */
  my_friendly_assert (TREE_CODE (d) == FUNCTION_DECL
                      || TREE_CODE (d) == VAR_DECL, 0);

  if (DECL_TEMPLATE_INSTANTIATED (d))
    /* D has already been instantiated.  It might seem reasonable to
       check whether or not D is an explict instantiation, and, if so,
       stop here.  But when an explicit instantiation is deferred
       until the end of the compilation, DECL_EXPLICIT_INSTANTIATION
       is set, even though we still need to do the instantiation.  */
    return d;

  /* If we already have a specialization of this declaration, then
     there's no reason to instantiate it.  Note that
     retrieve_specialization gives us both instantiations and
     specializations, so we must explicitly check
     DECL_TEMPLATE_SPECIALIZATION.  */
  gen_tmpl = most_general_template (tmpl);
  spec = retrieve_specialization (gen_tmpl, args);
  if (spec != NULL_TREE && DECL_TEMPLATE_SPECIALIZATION (spec))
    return spec;

  /* This needs to happen before any tsubsting.  */
  if (! push_tinst_level (d))
    return d;

  /* Set TD to the template whose DECL_TEMPLATE_RESULT is the pattern
     for the instantiation.  This is not always the most general
     template.  Consider, for example:

        template <class T>
        struct S { template <class U> void f();
                   template <> void f<int>(); };

     and an instantiation of S<double>::f<int>.  We want TD to be the
     specialization S<T>::f<int>, not the more general S<T>::f<U>.  */
  td = tmpl;
  for (td = tmpl;
       /* An instantiation cannot have a definition, so we need a
          more general template.  */
       DECL_TEMPLATE_INSTANTIATION (td)
         /* We must also deal with friend templates.  Given:

              template <class T> struct S { 
                template <class U> friend void f() {};
              };
         
            S<int>::f<U> say, is not an instantiation of S<T>::f<U>,
            so far as the language is concerned, but that's still
            where we get the pattern for the instantiation from.  On
            ther hand, if the definition comes outside the class, say:

              template <class T> struct S { 
                template <class U> friend void f();
              };
              template <class U> friend void f() {}

            we don't need to look any further.  That's what the check for
            DECL_INITIAL is for.  */
        || (TREE_CODE (d) == FUNCTION_DECL
            && DECL_FRIEND_PSEUDO_TEMPLATE_INSTANTIATION (td)
            && !DECL_INITIAL (DECL_TEMPLATE_RESULT (td)));
       )
    {
      /* The present template, TD, should not be a definition.  If it
         were a definition, we should be using it!  Note that we
         cannot restructure the loop to just keep going until we find
         a template with a definition, since that might go too far if
         a specialization was declared, but not defined.  */
      my_friendly_assert (!(TREE_CODE (d) == VAR_DECL
                            && !DECL_IN_AGGR_P (DECL_TEMPLATE_RESULT (td))), 
                          0); 
      
      /* Fetch the more general template.  */
      td = DECL_TI_TEMPLATE (td);
    }

  code_pattern = DECL_TEMPLATE_RESULT (td);

  if (TREE_CODE (d) == FUNCTION_DECL)
    pattern_defined = (DECL_INITIAL (code_pattern) != NULL_TREE);
  else
    pattern_defined = ! DECL_IN_AGGR_P (code_pattern);

  push_to_top_level ();
  lineno = DECL_SOURCE_LINE (d);
  input_filename = DECL_SOURCE_FILE (d);

  if (pattern_defined)
    {
      repo_template_used (d);

      if (flag_external_templates && ! DECL_INTERFACE_KNOWN (d))
        {
          if (flag_alt_external_templates)
            {
              if (interface_unknown)
                warn_if_unknown_interface (d);
            }
          else if (DECL_INTERFACE_KNOWN (code_pattern))
            {
              DECL_INTERFACE_KNOWN (d) = 1;
              DECL_NOT_REALLY_EXTERN (d) = ! DECL_EXTERNAL (code_pattern);
            }
          else
            warn_if_unknown_interface (code_pattern);
        }

      if (at_eof)
        import_export_decl (d);
    }

  /* Reject all external templates except inline functions.  */
  if (DECL_INTERFACE_KNOWN (d)
      && ! DECL_NOT_REALLY_EXTERN (d)
      && ! (TREE_CODE (d) == FUNCTION_DECL && DECL_INLINE (d)))
    goto out;

  if (TREE_CODE (d) == VAR_DECL 
      && TREE_READONLY (d)
      && DECL_INITIAL (d) == NULL_TREE
      && DECL_INITIAL (code_pattern) != NULL_TREE)
    /* We need to set up DECL_INITIAL regardless of pattern_defined if
         the variable is a static const initialized in the class body.  */;
  else if (! pattern_defined
           || (! (TREE_CODE (d) == FUNCTION_DECL && DECL_INLINE (d) && nested)
               && ! at_eof))
    {
      /* Defer all templates except inline functions used in another
         function.  We restore the source position here because it's used
         by add_pending_template.  */
      lineno = line;
      input_filename = file;

      if (at_eof && !pattern_defined 
          && DECL_EXPLICIT_INSTANTIATION (d))
        /* [temp.explicit]

           The definition of a non-exported function template, a
           non-exported member function template, or a non-exported
           member function or static data member of a class template
           shall be present in every translation unit in which it is
           explicitly instantiated.  */
        cp_error ("explicit instantiation of `%D' but no definition available",
                  d);

      add_pending_template (d);
      goto out;
    }

  /* We're now committed to instantiating this template.  Mark it as
     instantiated so that recursive calls to instantiate_decl do not
     try to instantiate it again.  */
  DECL_TEMPLATE_INSTANTIATED (d) = 1;

  /* Regenerate the declaration in case the template has been modified
     by a subsequent redeclaration.  */
  regenerate_decl_from_template (d, td);

  /* We already set the file and line above.  Reset them now in case
     they changed as a result of calling regenerate_decl_from_template.  */
  lineno = DECL_SOURCE_LINE (d);
  input_filename = DECL_SOURCE_FILE (d);

  if (TREE_CODE (d) == VAR_DECL)
    {
      DECL_IN_AGGR_P (d) = 0;
      if (DECL_INTERFACE_KNOWN (d))
        DECL_EXTERNAL (d) = ! DECL_NOT_REALLY_EXTERN (d);
      else
        {
          DECL_EXTERNAL (d) = 1;
          DECL_NOT_REALLY_EXTERN (d) = 1;
        }
      cp_finish_decl (d, DECL_INITIAL (d), NULL_TREE, 0, 0);
    }
  else if (TREE_CODE (d) == FUNCTION_DECL)
    {
      tree t = DECL_SAVED_TREE (code_pattern);

      start_function (NULL_TREE, d, NULL_TREE, 1);
      store_parm_decls ();

      if (t && TREE_CODE (t) == RETURN_INIT)
        {
          store_return_init
            (TREE_OPERAND (t, 0),
             tsubst_expr (TREE_OPERAND (t, 1), args, /*complain=*/1, tmpl));
          t = TREE_CHAIN (t);
        }

      if (t && TREE_CODE (t) == CTOR_INITIALIZER)
        {
          current_member_init_list
            = tsubst_expr_values (TREE_OPERAND (t, 0), args);
          current_base_init_list
            = tsubst_expr_values (TREE_OPERAND (t, 1), args);
          t = TREE_CHAIN (t);
        }

      setup_vtbl_ptr ();
      /* Always keep the BLOCK node associated with the outermost
         pair of curly braces of a function.  These are needed
         for correct operation of dwarfout.c.  */
      keep_next_level ();

      my_friendly_assert (TREE_CODE (t) == COMPOUND_STMT, 42);
      tsubst_expr (t, args, /*complain=*/1, tmpl);

      finish_function (lineno, 0, nested);
    }

out:
  lineno = line;
  input_filename = file;

  pop_from_top_level ();
  pop_tinst_level ();

  return d;
}

/* Substitute ARGVEC into T, which is a TREE_LIST.  In particular, it
   is an initializer list: the TREE_PURPOSEs are DECLs, and the
   TREE_VALUEs are initializer values.  Used by instantiate_decl.  */

static tree
tsubst_expr_values (t, argvec)
     tree t, argvec;
{
  tree first = NULL_TREE;
  tree *p = &first;

  for (; t; t = TREE_CHAIN (t))
    {
      tree pur = tsubst_copy (TREE_PURPOSE (t), argvec,
                              /*complain=*/1, NULL_TREE);
      tree val = tsubst_expr (TREE_VALUE (t), argvec, /*complain=*/1, 
                              NULL_TREE);
      *p = build_tree_list (pur, val);
      p = &TREE_CHAIN (*p);
    }
  return first;
}

tree last_tree;

void
add_tree (t)
     tree t;
{
  last_tree = TREE_CHAIN (last_tree) = t;
}


void
begin_tree ()
{
  saved_trees = tree_cons (NULL_TREE, last_tree, saved_trees);
  last_tree = NULL_TREE;
}


void 
end_tree ()
{
  my_friendly_assert (saved_trees != NULL_TREE, 0);

  last_tree = TREE_VALUE (saved_trees);
  saved_trees = TREE_CHAIN (saved_trees);
}

/* D is an undefined function declaration in the presence of templates with
   the same name, listed in FNS.  If one of them can produce D as an
   instantiation, remember this so we can instantiate it at EOF if D has
   not been defined by that time.  */

void
add_maybe_template (d, fns)
     tree d, fns;
{
  tree t;

  if (DECL_MAYBE_TEMPLATE (d))
    return;

  t = most_specialized (fns, d, NULL_TREE);
  if (! t)
    return;
  if (t == error_mark_node)
    {
      cp_error ("ambiguous template instantiation for `%D'", d);
      return;
    }

  *maybe_template_tail = perm_tree_cons (t, d, NULL_TREE);
  maybe_template_tail = &TREE_CHAIN (*maybe_template_tail);
  DECL_MAYBE_TEMPLATE (d) = 1;
}

/* Set CURRENT_ACCESS_SPECIFIER based on the protection of DECL.  */

static void
set_current_access_from_decl (decl)
     tree decl;
{
  if (TREE_PRIVATE (decl))
    current_access_specifier = access_private_node;
  else if (TREE_PROTECTED (decl))
    current_access_specifier = access_protected_node;
  else
    current_access_specifier = access_public_node;
}

/* Instantiate an enumerated type.  TAG is the template type, NEWTAG
   is the instantiation (which should have been created with
   start_enum) and ARGS are the template arguments to use.  */

static void
tsubst_enum (tag, newtag, args)
     tree tag;
     tree newtag;
     tree args;
{
  tree e;

  for (e = TYPE_VALUES (tag); e; e = TREE_CHAIN (e))
    {
      tree value;
      tree elt;

      /* Note that in a template enum, the TREE_VALUE is the
         CONST_DECL, not the corresponding INTEGER_CST.  */
      value = tsubst_expr (DECL_INITIAL (TREE_VALUE (e)), 
                           args, /*complain=*/1,
                           NULL_TREE);

      /* Give this enumeration constant the correct access.  */
      set_current_access_from_decl (TREE_VALUE (e));

      /* Actually build the enumerator itself.  */
      elt = build_enumerator (TREE_PURPOSE (e), value, newtag); 

      /* We save the enumerators we have built so far in the
         TYPE_VALUES so that if the enumeration constants for
         subsequent enumerators involve those for previous ones,
         tsubst_copy will be able to find them.  */
      TREE_CHAIN (elt) = TYPE_VALUES (newtag);
      TYPE_VALUES (newtag) = elt;
    }

  finish_enum (newtag);
}

/* Set the DECL_ASSEMBLER_NAME for DECL, which is a FUNCTION_DECL that
   is either an instantiation or specialization of a template
   function.  */

static void
set_mangled_name_for_template_decl (decl)
     tree decl;
{
  tree saved_namespace;
  tree context = NULL_TREE;
  tree fn_type;
  tree ret_type;
  tree parm_types;
  tree tparms;
  tree targs;
  tree tmpl;
  int parm_depth;

  my_friendly_assert (TREE_CODE (decl) == FUNCTION_DECL, 0);
  my_friendly_assert (DECL_TEMPLATE_INFO (decl) != NULL_TREE, 0);

  /* The names of template functions must be mangled so as to indicate
     what template is being specialized with what template arguments.
     For example, each of the following three functions must get
     different mangled names:

       void f(int);                  
       template <> void f<7>(int);
       template <> void f<8>(int);  */

  targs = DECL_TI_ARGS (decl);
  if (uses_template_parms (targs))
    /* This DECL is for a partial instantiation.  There's no need to
       mangle the name of such an entity.  */
    return;

  tmpl = most_general_template (DECL_TI_TEMPLATE (decl));
  tparms = DECL_TEMPLATE_PARMS (tmpl);
  parm_depth = TMPL_PARMS_DEPTH (tparms);

  /* There should be as many levels of arguments as there are levels
     of parameters.  */
  my_friendly_assert (parm_depth == TMPL_ARGS_DEPTH (targs), 0);

  /* We now compute the PARMS and RET_TYPE to give to
     build_decl_overload_real.  The PARMS and RET_TYPE are the
     parameter and return types of the template, after all but the
     innermost template arguments have been substituted, not the
     parameter and return types of the function DECL.  For example,
     given:

       template <class T> T f(T);

     both PARMS and RET_TYPE should be `T' even if DECL is `int f(int)'.  
     A more subtle example is:

       template <class T> struct S { template <class U> void f(T, U); }

     Here, if DECL is `void S<int>::f(int, double)', PARMS should be
     {int, U}.  Thus, the args that we want to subsitute into the
     return and parameter type for the function are those in TARGS,
     with the innermost level omitted.  */
  fn_type = TREE_TYPE (tmpl);
  if (DECL_STATIC_FUNCTION_P (decl))
    context = DECL_CLASS_CONTEXT (decl);

  if (parm_depth == 1)
    /* No substitution is necessary.  */
    ;
  else
    {
      int i;
      tree partial_args;

      /* Replace the innermost level of the TARGS with NULL_TREEs to
         let tsubst know not to subsitute for those parameters.  */
      partial_args = make_temp_vec (TREE_VEC_LENGTH (targs));
      for (i = 1; i < TMPL_ARGS_DEPTH (targs); ++i)
        SET_TMPL_ARGS_LEVEL (partial_args, i,
                             TMPL_ARGS_LEVEL (targs, i));
      SET_TMPL_ARGS_LEVEL (partial_args,
                           TMPL_ARGS_DEPTH (targs),
                           make_temp_vec (DECL_NTPARMS (tmpl)));

      /* Now, do the (partial) substitution to figure out the
         appropriate function type.  */
      fn_type = tsubst (fn_type, partial_args, /*complain=*/1, NULL_TREE);
      if (DECL_STATIC_FUNCTION_P (decl))
        context = tsubst (context, partial_args, /*complain=*/1, NULL_TREE);

      /* Substitute into the template parameters to obtain the real
         innermost set of parameters.  This step is important if the
         innermost set of template parameters contains value
         parameters whose types depend on outer template parameters.  */
      TREE_VEC_LENGTH (partial_args)--;
      tparms = tsubst_template_parms (tparms, partial_args, /*complain=*/1);
    }

  /* Now, get the innermost parameters and arguments, and figure out
     the parameter and return types.  */
  tparms = INNERMOST_TEMPLATE_PARMS (tparms);
  targs = innermost_args (targs);
  ret_type = TREE_TYPE (fn_type);
  parm_types = TYPE_ARG_TYPES (fn_type);

  /* For a static member function, we generate a fake `this' pointer,
     for the purposes of mangling.  This indicates of which class the
     function is a member.  Because of:

       [class.static] 

       There shall not be a static and a nonstatic member function
       with the same name and the same parameter types

     we don't have to worry that this will result in a clash with a
     non-static member function.  */
  if (DECL_STATIC_FUNCTION_P (decl))
    parm_types = hash_tree_chain (build_pointer_type (context), parm_types);

  /* There should be the same number of template parameters as
     template arguments.  */
  my_friendly_assert (TREE_VEC_LENGTH (tparms) == TREE_VEC_LENGTH (targs),
                      0);

  /* If the template is in a namespace, we need to put that into the
     mangled name. Unfortunately, build_decl_overload_real does not
     get the decl to mangle, so it relies on the current
     namespace. Therefore, we set that here temporarily. */
  my_friendly_assert (TREE_CODE_CLASS (TREE_CODE (decl)) == 'd', 980702);
  saved_namespace = current_namespace;
  current_namespace = CP_DECL_CONTEXT (decl);  

  /* Actually set the DCL_ASSEMBLER_NAME.  */
  DECL_ASSEMBLER_NAME (decl)
    = build_decl_overload_real (DECL_NAME (decl), parm_types, ret_type,
                                tparms, targs, 
                                DECL_FUNCTION_MEMBER_P (decl) 
                                + DECL_CONSTRUCTOR_P (decl));

  /* Restore the previously active namespace.  */
  current_namespace = saved_namespace;
}