* pt.c (determine_specialization): Give better errors.

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

/* Handle parameterized types (templates) for GNU C++.
   Copyright (C) 1992, 93, 94, 95, 96, 1997 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 <stdio.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"

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif

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;
static int template_header_count;

static tree saved_trees;

#define obstack_chunk_alloc xmalloc
#define obstack_chunk_free free

static int unify PROTO((tree, tree *, int, tree, tree, int *, 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, tree));
static tree tsubst_expr_values PROTO((tree, tree));
static int comp_template_args 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 tree tsubst_enum PROTO((tree, tree, int, tree *));
static tree add_to_template_args PROTO((tree, tree));
static int  type_unification_real PROTO((tree, tree *, tree, tree, int*,
                                         int, int, int));
static void note_template_header PROTO((int));
static tree maybe_fold_nontype_arg PROTO((tree));
static tree convert_nontype_argument PROTO((tree, tree));

/* 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 (template_parameters, decl)
  tree template_parameters;
  tree decl;
{
  if (template_parameters)
    end_template_decl();
  else
    end_specialization();

  if (decl && DECL_TEMPLATE_INFO (decl) &&
      !DECL_TEMPLATE_SPECIALIZATION (decl))
    {
      check_member_template (DECL_TI_TEMPLATE (decl));
      return DECL_TI_TEMPLATE (decl);
    }

  if (decl)
    return decl;

  cp_error ("invalid member template declaration");
  return NULL_TREE;
}

/* Restore the template parameter context. */

void 
begin_member_template_processing (decl)
     tree decl;
{
  tree parms;
  int i;

  parms = DECL_INNERMOST_TEMPLATE_PARMS (DECL_TI_TEMPLATE (decl));

  ++processing_template_decl;
  current_template_parms 
    = tree_cons (build_int_2 (0, processing_template_decl),
                 parms, current_template_parms);
  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. */
            tree decl = build_decl (CONST_DECL, DECL_NAME (parm),
                                    TREE_TYPE (parm));
            DECL_INITIAL (decl) = DECL_INITIAL (parm);
            pushdecl (decl);
          }
        break;

        default:
          my_friendly_abort (0);
        }
    }
}

/* Undo the effects of begin_member_template_processing. */

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

  --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.  */

int
is_member_template (t)
     tree t;
{
  int r = 0;

  if (TREE_CODE (t) != FUNCTION_DECL
      && !DECL_FUNCTION_TEMPLATE_P (t))
    /* Anything that isn't a function or a template function is
       certainly not a member template.  */
    return 0;

  if ((DECL_FUNCTION_MEMBER_P (t) 
       && !DECL_TEMPLATE_SPECIALIZATION (t))
      || (TREE_CODE (t) == TEMPLATE_DECL && 
          DECL_FUNCTION_MEMBER_P (DECL_TEMPLATE_RESULT (t))))
    {
      tree tmpl = NULL_TREE;

      if (DECL_FUNCTION_TEMPLATE_P (t))
        tmpl = t;
      else if (DECL_TEMPLATE_INFO (t) 
               && DECL_FUNCTION_TEMPLATE_P (DECL_TI_TEMPLATE (t)))
        tmpl = DECL_TI_TEMPLATE (t);

      if (tmpl) 
        {
          tree parms = DECL_TEMPLATE_PARMS (tmpl);
          int parm_levels = list_length (parms);
          int template_class_levels = 0;
          tree ctx = DECL_CLASS_CONTEXT (t);

          /* NB - The code below does not yet handle template class
             members, e.g. 
             
               template <class T> class C { template <class U> class D; }}

             correctly.  In that case, the D should have level 2.  */

          if (CLASSTYPE_TEMPLATE_INFO (ctx))
            {
              tree args = CLASSTYPE_TI_ARGS (ctx);
              int i;
              
              if (args == NULL_TREE)
                template_class_levels = 1;
              else 
                for (i = 0; i < TREE_VEC_LENGTH (args); ++i)
                  if (uses_template_parms (TREE_VEC_ELT (args, i)))
                    {
                      template_class_levels++;
                      break;
                    }
            }

          if (parm_levels > template_class_levels)
            r = 1;
        }
    }

  return r;
}

/* Return a new template argument vector which contains all of ARGS,
   but has as its innermost set of arguments the EXTRA_ARGS.  */

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

  if (TREE_CODE (TREE_VEC_ELT (args, 0)) != TREE_VEC)
    {
      new_args = make_tree_vec (2);
      TREE_VEC_ELT (new_args, 0) = args;
    }
  else 
    {
      int i;

      new_args = make_tree_vec (TREE_VEC_LENGTH (args) - 1);

      for (i = 0; i < TREE_VEC_LENGTH (args); ++i)
        TREE_VEC_ELT (new_args, i) = TREE_VEC_ELT (args, i);
    }
          
  TREE_VEC_ELT (new_args, 
                TREE_VEC_LENGTH (new_args) - 1) = 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 ()
{
  pushlevel (0);
  declare_pseudo_global_level ();
  ++processing_template_decl;
  note_template_header (0);
}


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

void
begin_specialization ()
{
  note_template_header (1);
}


/* 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;
}


/* 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);

  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;
}



/* Register the specialization SPEC as a specialization of TMPL with
   the indicated ARGS.  */

static void
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) != TEMPLATE_DECL
      && list_length (DECL_TEMPLATE_PARMS (tmpl)) > 1)
    /* Avoid registering function declarations as
       specializations of member templates, as would otherwise
       happen with out-of-class specializations of member
       templates.  */
    return;
    
  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;
                  }
                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 of
                       class type, and then specialized it later.  */
                    TREE_VALUE (s) = spec;
                    return;
                  }
              }
            else if (DECL_TEMPLATE_SPECIALIZATION (fn))
              {
                if (DECL_INITIAL (fn))
                  cp_error ("duplicate specialization of %D", fn);

                TREE_VALUE (s) = spec;
                return;
              }
          }
      }

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


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

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

  char* str = "candidates are:";

  for (fn = fns; fn != NULL_TREE; fn = TREE_CHAIN (fn))
    {
      cp_error_at ("%s %+#D", str, TREE_VALUE (fn));
      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.  If
   NEED_MEMBER_TEMPLATE is true the function is 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, unless COMPLAIN is 0.  The DECL may be NULL_TREE if none is
   available.  */

tree
determine_specialization (template_id, decl, targs_out, 
                          need_member_template,
                          complain)
     tree template_id;
     tree decl;
     tree* targs_out;
     int need_member_template;
     int complain;
{
  tree fns = TREE_OPERAND (template_id, 0);
  tree targs_in = TREE_OPERAND (template_id, 1);
  tree templates = NULL_TREE;
  tree fn;
  int overloaded;
  int i;

  *targs_out = NULL_TREE;

  if (is_overloaded_fn (fns))
    fn = get_first_fn (fns);
  else
    fn = NULL_TREE;

  overloaded = really_overloaded_fn (fns);
  for (; fn != NULL_TREE; 
       fn = overloaded ? DECL_CHAIN (fn) : NULL_TREE)
    {
      int dummy = 0;
      tree tmpl;

      if (!need_member_template 
          && TREE_CODE (fn) == FUNCTION_DECL 
          && DECL_FUNCTION_MEMBER_P (fn)
          && DECL_USE_TEMPLATE (fn)
          && DECL_TI_TEMPLATE (fn))
        /* We can get here when processing something like:
             template <class T> class X { void f(); }
             template <> void X<int>::f() {}
           We're specializing a member function, but not a member
           template.  */
        tmpl = DECL_TI_TEMPLATE (fn);
      else if (TREE_CODE (fn) != TEMPLATE_DECL
               || (need_member_template && !is_member_template (fn)))
        {
          if (decls_match (decl, fn))
            {
              cp_error ("`template <>' applied to non-specialization `%D'",
                        fn);
              return NULL_TREE;
            }
          continue;
        }
      else
        tmpl = fn;

      if (list_length (targs_in) > DECL_NTPARMS (tmpl))
        continue;

      if (decl == NULL_TREE)
        {
          tree targs = make_scratch_vec (DECL_NTPARMS (tmpl));

          /* We allow incomplete unification here, because we are going to
             check all the functions. */
          i = type_unification (DECL_INNERMOST_TEMPLATE_PARMS (tmpl),
                                &TREE_VEC_ELT (targs, 0),
                                NULL_TREE,
                                NULL_TREE,  
                                targs_in,
                                &dummy, 1, 1);
      
          if (i == 0) 
            /* Unification was successful.  */
            templates = scratch_tree_cons (targs, tmpl, templates);
        }
      else
        templates = scratch_tree_cons (NULL_TREE, tmpl, templates);
    }
  
  if (decl != NULL_TREE)
    {
      tree tmpl = most_specialized (templates, decl, targs_in);

      if (tmpl == error_mark_node) 
        goto ambiguous;
      else if (tmpl == NULL_TREE)
        goto no_match;

      *targs_out = get_bindings (tmpl, decl, targs_in);
      return tmpl;
    }

  if (templates == NULL_TREE)
    {
    no_match:
      if (complain)
        cp_error ("`%D' does not match any template declaration", decl);
      
      return NULL_TREE;
    }
  else if (TREE_CHAIN (templates) != NULL_TREE) 
    {
    ambiguous:
      if (complain)
        {
          cp_error ("ambiguous template specialization `%D'", decl);
          print_candidates (templates);
        }
      return NULL_TREE;
    }

  /* We have one, and exactly one, match. */
  *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. 
   
     0: The function is not an explicit specialization or instantiation.
     1: The function is an explicit specialization.
     2: The function is an explicit instantiation.

   FLAGS is a bitmask consisting of the following flags: 

   1: We are being called by finish_struct.  (We are unable to
      determine what template is specialized by an in-class
      declaration until the class definition is complete, so
      finish_struct_methods calls this function again later to finish
      the job.)
   2: The function has a definition.
   4: The function is a friend.
   8: The function is known to be a specialization of a member
      template. 

   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 finish_member = flags & 1;
  int have_def = flags & 2;
  int is_friend = flags & 4;
  int specialization = 0;
  int explicit_instantiation = 0;
  int member_specialization = flags & 8;

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

  if (!finish_member)
    {
      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))
        {
          /* 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)
        {
          /* 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 || explicit_instantiation)
    {
      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_GLOBAL_VALUE (dname);
          else
            fns = dname;

          declarator = 
            lookup_template_function (fns, NULL_TREE);
        }

      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))
        {
          /* Since finish_struct_1 has not been called yet, we
             can't call lookup_fnfields.  We note that this
             template is a specialization, and proceed, letting
             finish_struct fix this up later.  */
          tree ti = perm_tree_cons (NULL_TREE, 
                                    TREE_OPERAND (declarator, 1),
                                    NULL_TREE);
          TI_PENDING_SPECIALIZATION_FLAG (ti) = 1;
          DECL_TEMPLATE_INFO (decl) = ti;
          /* This should not be an instantiation; explicit
             instantiation directives can only occur at the top
             level.  */
          my_friendly_assert (!explicit_instantiation, 0);
          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;
          
          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 decl;
                }

              fns = TREE_VEC_ELT(CLASSTYPE_METHOD_VEC (ctype),
                                 is_constructor ? 0 : 1);
            }
          else 
            fns = lookup_fnfields (TYPE_BINFO (ctype), name,
                                   1);
          
          if (fns == NULL_TREE) 
            {
              cp_error ("no member function `%s' declared in `%T'",
                        IDENTIFIER_POINTER (name),
                        ctype);
              return decl;
            }
          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 the
         instantiation is for a member template, or just a member
         function of a template class.  In particular, even in if the
         instantiation is for a member template, the template
         arguments could be deduced from the declaration.  */
      tmpl = determine_specialization (declarator, decl,
                                       &targs, 
                                       member_specialization,
                                       1);
            
      if (tmpl)
        {
          if (explicit_instantiation)
            {
              decl = instantiate_template (tmpl, targs);
              if (!DECL_TEMPLATE_SPECIALIZATION (decl))
                /* There doesn't seem to be anything in the draft to
                   prevent a specialization from being explicitly
                   instantiated.  We're careful not to destroy the
                   information indicating that this is a
                   specialization here.  */
                SET_DECL_EXPLICIT_INSTANTIATION (decl);
              return decl;
            }
          else if (DECL_STATIC_FUNCTION_P (tmpl)
                   && DECL_NONSTATIC_MEMBER_FUNCTION_P (decl))
            revert_static_member_fn (&decl, 0, 0);

          /* 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.  */
          if ((is_member_template (tmpl) || ctype == NULL_TREE)
              && name_mangling_version >= 1)
            {
              tree arg_types = TYPE_ARG_TYPES (TREE_TYPE (tmpl));

              if (ctype 
                  && TREE_CODE (TREE_TYPE (tmpl)) == FUNCTION_TYPE)
                arg_types = 
                  hash_tree_chain (build_pointer_type (ctype),
                                   arg_types);

              DECL_ASSEMBLER_NAME (decl) 
                = build_template_decl_overload 
                (DECL_NAME (decl), 
                 arg_types,
                 TREE_TYPE (TREE_TYPE (tmpl)),
                 DECL_INNERMOST_TEMPLATE_PARMS (tmpl),
                 targs, ctype != NULL_TREE);
            }

          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);
              DECL_TEMPLATE_INFO (decl) 
                = perm_tree_cons (tmpl, targs, NULL_TREE);
              return decl;
            }

          /* If DECL_TI_TEMPLATE (decl), the decl is an
             instantiation of a specialization of a member template.
             (In other words, there was a member template, in a
             class template.  That member template was specialized.
             We then instantiated the class, so there is now an
             instance of that specialization.)  

             According to the CD2,

             14.7.3.13 [tmpl.expl.spec]
               
             A specialization  of  a member function template or
             member class template of a non-specialized class
             template is itself a template.             

             So, we just leave the template info alone in this case.  */
          if (!(DECL_TEMPLATE_INFO (decl) && DECL_TI_TEMPLATE (decl)))
            DECL_TEMPLATE_INFO (decl)
              = perm_tree_cons (tmpl, targs, NULL_TREE);

          register_specialization (decl, tmpl, targs);

          return decl;
        }
    }
  
  return decl;
}


/* 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 (!comptypes (TREE_TYPE (parm1), 
                               TREE_TYPE (parm2), 1))
            return 0;
        }
    }

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

  return 1;
}


/* 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_CONST_IDX (DECL_INITIAL (p));
      ++idx;
    }
  else
    idx = 0;

  if (!is_type)
    {
      tree tinfo = 0;
      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);
      /* 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)
        {
          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));
      tinfo = make_node (TEMPLATE_CONST_PARM);
      my_friendly_assert (TREE_PERMANENT (tinfo), 260.5);
      if (TREE_PERMANENT (parm) == 0)
        {
          parm = copy_node (parm);
          TREE_PERMANENT (parm) = 1;
        }
      TREE_TYPE (tinfo) = TREE_TYPE (parm);
      decl = build_decl (CONST_DECL, DECL_NAME (parm), TREE_TYPE (parm));
      DECL_INITIAL (decl) = tinfo;
      DECL_INITIAL (parm) = tinfo;
      TEMPLATE_CONST_SET_INFO (tinfo, idx, processing_template_decl);
    }
  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);
        }
        
      CLASSTYPE_GOT_SEMICOLON (t) = 1;
      TYPE_NAME (t) = decl;
      TYPE_STUB_DECL (t) = decl;
      parm = decl;
      TEMPLATE_TYPE_SET_INFO (t, idx, processing_template_decl);
    }
  SET_DECL_ARTIFICIAL (decl);
  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;

  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? */
}

/* Generate a valid set of template args from current_template_parms.  */

tree
current_template_args ()
{
  tree header = current_template_parms;
  int length = list_length (header);
  tree args = make_tree_vec (length);
  int l = length;

  while (header)
    {
      tree a = copy_node (TREE_VALUE (header));
      int i = TREE_VEC_LENGTH (a);
      TREE_TYPE (a) = NULL_TREE;
      while (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;
        }
      TREE_VEC_ELT (args, --l) = a;
      header = TREE_CHAIN (header);
    }

  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;
}

  
/* 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.  */

tree
push_template_decl (decl)
     tree decl;
{
  tree tmpl;
  tree args = NULL_TREE;
  tree info;
  tree ctx = DECL_CONTEXT (decl) ? DECL_CONTEXT (decl) : current_class_type;
  int primary = 0;

  /* Kludge! */
  if (TREE_CODE (decl) == FUNCTION_DECL && DECL_FRIEND_P (decl)
      && DECL_CLASS_CONTEXT (decl))
    ;
  /* Note that this template is a "primary template" */
  else if (! ctx 
           || (TREE_CODE_CLASS (TREE_CODE (ctx)) == 't' 
               && ! CLASSTYPE_TEMPLATE_INFO (ctx))
      /* || (processing_template_decl > CLASSTYPE_TEMPLATE_LEVEL (ctx)) */)
    primary = 1;

  /* Partial specialization.  */
  if (TREE_CODE (decl) == TYPE_DECL && DECL_ARTIFICIAL (decl)
      && CLASSTYPE_TEMPLATE_SPECIALIZATION (TREE_TYPE (decl)))
    {
      tree type = TREE_TYPE (decl);
      tree maintmpl = CLASSTYPE_TI_TEMPLATE (type);
      tree mainargs = CLASSTYPE_TI_ARGS (type);
      tree spec = DECL_TEMPLATE_SPECIALIZATIONS (maintmpl);

      for (; spec; spec = TREE_CHAIN (spec))
        {
          /* purpose: args to main template
             value: spec template */
          if (comp_template_args (TREE_PURPOSE (spec), mainargs))
            return decl;
        }

      DECL_TEMPLATE_SPECIALIZATIONS (maintmpl) = CLASSTYPE_TI_SPEC_INFO (type)
        = perm_tree_cons (mainargs, TREE_VALUE (current_template_parms),
                          DECL_TEMPLATE_SPECIALIZATIONS (maintmpl));
      TREE_TYPE (DECL_TEMPLATE_SPECIALIZATIONS (maintmpl)) = type;
      return decl;
    }

  args = current_template_args ();

  if (! ctx || TREE_CODE (ctx) == FUNCTION_DECL 
      || TYPE_BEING_DEFINED (ctx))
    {
      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 t;
      tree a;

      if (CLASSTYPE_TEMPLATE_INSTANTIATION (ctx))
        cp_error ("must specialize `%#T' before defining member `%#D'",
                  ctx, decl);
      if (TREE_CODE (decl) == TYPE_DECL && DECL_ARTIFICIAL (decl))
        tmpl = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (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))
        {
          if (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;
            }
          
          a = TREE_VEC_ELT (args, TREE_VEC_LENGTH (args) - 1);
          t = DECL_INNERMOST_TEMPLATE_PARMS (DECL_TI_TEMPLATE (decl));
          if (TREE_VEC_LENGTH (t) 
              != TREE_VEC_LENGTH (a))
            {
              cp_error ("got %d template parameters for `%#D'",
                        TREE_VEC_LENGTH (a), decl);
              cp_error ("  but %d required", TREE_VEC_LENGTH (t));
            }
          if (TREE_VEC_LENGTH (args) > 1)
            /* Get the template parameters for the enclosing template
               class.  */ 
            a = TREE_VEC_ELT (args, TREE_VEC_LENGTH (args) - 2);
          else
            a = NULL_TREE;
        }
      else 
        a = TREE_VEC_ELT (args, TREE_VEC_LENGTH (args) - 1);

      t = NULL_TREE;

      if (CLASSTYPE_TEMPLATE_SPECIALIZATION (ctx))
        {
          /* When processing an inline member template of a
             specialized class, there is no CLASSTYPE_TI_SPEC_INFO.  */
          if (CLASSTYPE_TI_SPEC_INFO (ctx))
            t = TREE_VALUE (CLASSTYPE_TI_SPEC_INFO (ctx));
        }
      else if (CLASSTYPE_TEMPLATE_INFO (ctx))
        t = DECL_INNERMOST_TEMPLATE_PARMS (CLASSTYPE_TI_TEMPLATE (ctx));

      /* There should be template arguments if and only if there is a
         template class.  */
      my_friendly_assert((a != NULL_TREE) == (t != NULL_TREE), 0);

      if (t != NULL_TREE 
          && TREE_VEC_LENGTH (t) != TREE_VEC_LENGTH (a))
        {
          cp_error ("got %d template parameters for `%#D'",
                    TREE_VEC_LENGTH (a), decl);
          cp_error ("  but `%#T' has %d", ctx, TREE_VEC_LENGTH (t));
        }
    }
  /* Get the innermost set of template arguments. */
  args = TREE_VEC_ELT (args, TREE_VEC_LENGTH (args) - 1);

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

  if (! ctx)
    tmpl = pushdecl_top_level (tmpl);

  if (primary)
    TREE_TYPE (DECL_INNERMOST_TEMPLATE_PARMS (tmpl)) = tmpl;

  info = perm_tree_cons (tmpl, args, NULL_TREE);

  if (TREE_CODE (decl) == TYPE_DECL && DECL_ARTIFICIAL (decl))
    {
      CLASSTYPE_TEMPLATE_INFO (TREE_TYPE (tmpl)) = info;
      if (!ctx || TREE_CODE (ctx) != FUNCTION_DECL)
        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);
}


/* 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 (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))
        {
          cp_error ("non-constant `%E' cannot be used as template argument",
                    expr);
          return NULL_TREE;
        }
    }
  else if (TYPE_PTR_P (expr_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;

      if (TREE_CODE (expr) != 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 (expr, 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 (TREE_CODE (expr) == VAR_DECL)
    {
      if (!TREE_PUBLIC (expr))
        goto bad_argument;
    }
  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.  */
      return digest_init (type, expr, (tree*) 0);

    case REAL_TYPE:
    case COMPLEX_TYPE:
      /* These are g++ extensions.  */
      if (TREE_CODE (expr_type) != TREE_CODE (type))
        return error_mark_node;

      return digest_init (type, expr, (tree*) 0);

    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 (comptypes (type, TREE_TYPE (expr), 1), 
                                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 (!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;
              }

            if (fn == error_mark_node)
              return error_mark_node;

            my_friendly_assert (comptypes (type, TREE_TYPE (fn), 1),
                                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 (!comptypes (TYPE_MAIN_VARIANT (expr_type),
                            TYPE_MAIN_VARIANT (type), 1)
                || (TYPE_READONLY (expr_type) >
                    TYPE_READONLY (type_referred_to))
                || (TYPE_VOLATILE (expr_type) >
                    TYPE_VOLATILE (type_referred_to))
                || !real_lvalue_p (expr))
              return error_mark_node;
            else
              return expr;
          }
      }
      break;

    case RECORD_TYPE:
      {
        tree fns;
        tree fn;

        my_friendly_assert (TYPE_PTRMEMFUNC_P (type), 0);

        /* 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 (!comptypes (type, expr_type, 1))
              return error_mark_node;
            else 
              return expr;
          }

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

        fns = TREE_OPERAND (expr, 0);
        
        fn = instantiate_type (TREE_TYPE (TREE_TYPE (type)), 
                               fns, 0);
        
        if (fn == error_mark_node)
          return error_mark_node;

        expr = build_unary_op (ADDR_EXPR, fn, 0);
        
        my_friendly_assert (comptypes (type, TREE_TYPE (expr), 1), 
                            0);
        return expr;
      }
      break;

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

  return error_mark_node;
}

/* Convert all template arguments to their appropriate types, and return
   a vector containing the resulting values.  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.  */

static tree
coerce_template_parms (parms, arglist, in_decl,
                       complain,
                       require_all_arguments)
     tree parms, arglist;
     tree in_decl;
     int complain;
     int require_all_arguments;
{
  int nparms, nargs, i, lost = 0;
  int is_tmpl_parm = 0;
  tree vec = NULL_TREE;

  if (arglist == NULL_TREE)
    nargs = 0;
  else if (TREE_CODE (arglist) == TREE_VEC)
    nargs = TREE_VEC_LENGTH (arglist);
  else
    nargs = list_length (arglist);

  nparms = TREE_VEC_LENGTH (parms);

  if (nargs > nparms
      || (nargs < nparms
          && require_all_arguments
          && TREE_PURPOSE (TREE_VEC_ELT (parms, nargs)) == NULL_TREE))
    {
      if (complain) 
        {
          error ("incorrect number of parameters (%d, should be %d)",
                 nargs, nparms);
          
          if (in_decl)
            cp_error_at ("in template expansion for decl `%D'",
                         in_decl);
        }

      return error_mark_node;
    }

  if (arglist && TREE_CODE (arglist) == TREE_VEC && nargs == nparms)
    vec = copy_node (arglist);
  else
    {
      /* We can arrive here with arglist being a TREE_VEC when a 
         template with some default arguments is used as template 
         template argument.  */
      is_tmpl_parm = TREE_CODE (arglist) == TREE_VEC;
      vec = make_tree_vec (nparms);

      for (i = 0; i < nparms; i++)
        {
          tree arg;
          tree parm = TREE_VEC_ELT (parms, i);

          if (arglist)
            {
              arg = arglist;
              arglist = TREE_CHAIN (arglist);

              if (arg == error_mark_node)
                lost++;
              else
                arg = TREE_VALUE (arg);
            }
          else if (is_tmpl_parm && i < nargs)
            {
              arg = TREE_VEC_ELT (arglist, i);
              if (arg == error_mark_node)
                lost++;
            }
          else if (TREE_PURPOSE (parm) == NULL_TREE)
            {
              my_friendly_assert (!require_all_arguments, 0);
              break;
            }
          else if (TREE_CODE (TREE_VALUE (parm)) == TYPE_DECL)
            arg = tsubst (TREE_PURPOSE (parm), vec, i, in_decl);
          else
            arg = tsubst_expr (TREE_PURPOSE (parm), vec, i, in_decl);

          TREE_VEC_ELT (vec, i) = arg;
        }
    }
  for (i = 0; i < nparms; i++)
    {
      tree arg = TREE_VEC_ELT (vec, i);
      tree parm = TREE_VALUE (TREE_VEC_ELT (parms, i));
      tree val = 0;
      int is_type, requires_type, is_tmpl_type, requires_tmpl_type;

      if (arg == NULL_TREE)
        /* We're out of arguments.  */
        {
          my_friendly_assert (!require_all_arguments, 0);
          break;
        }

      if (arg == error_mark_node)
        {
          cp_error ("template argument %d is invalid", i + 1);
          lost++;
          continue;
        }

      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;
        }
      else if (TREE_CODE (arg) == TREE_LIST && ! is_overloaded_fn (arg))
        {
          /* In case we are checking arguments inside a template template
             parameter, ARG that does not come from default argument is 
             also a TREE_LIST node */
          is_tmpl_parm = 1;
          arg = TREE_VALUE (arg);
        }

      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.  */
      is_tmpl_type = (TREE_CODE (arg) == TEMPLATE_DECL
                      && TREE_CODE (DECL_TEMPLATE_RESULT (arg)) == TYPE_DECL)
                     || (TREE_CODE (arg) == TEMPLATE_TEMPLATE_PARM
                         && !CLASSTYPE_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);
      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
                || (is_tmpl_parm && TREE_CODE (arg) == TYPE_DECL);

      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);
                }
            }
          lost++;
          TREE_VEC_ELT (vec, i) = error_mark_node;
          continue;
        }
      if (is_tmpl_type ^ requires_tmpl_type)
        {
          if (in_decl)
            {
              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);
            }
          lost++;
          TREE_VEC_ELT (vec, i) = error_mark_node;
          continue;
        }
      if (is_tmpl_parm)
        {
          if (requires_tmpl_type)
            {
              cp_error ("nested template template parameter not implemented");
              lost++;
              TREE_VEC_ELT (vec, i) = error_mark_node;
            }
          continue;
        }
        
      if (is_type)
        {
          if (requires_tmpl_type)
            {
              tree parmparm = DECL_INNERMOST_TEMPLATE_PARMS (parm);
              tree argparm = DECL_INNERMOST_TEMPLATE_PARMS (arg);

              /* 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 Allcator = allocator> 
                   class vector.  */

              val = coerce_template_parms (argparm, parmparm, in_decl, 1, 1);
              if (val != error_mark_node)
                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
            {
              val = groktypename (arg);
              if (! processing_template_decl)
                {
                  tree t = target_type (val);
                  if (TREE_CODE (t) != TYPENAME_TYPE 
                      && IS_AGGR_TYPE (t)
                      && decl_function_context (TYPE_MAIN_DECL (t)))
                    {
                      cp_error ("type `%T' composed from a local class is not a valid template-argument",
                                val);
                      return error_mark_node;
                    }
                }
            }
        }
      else
        {
          tree t = tsubst (TREE_TYPE (parm), vec,
                           TREE_VEC_LENGTH (vec), 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);
        }

      if (val == error_mark_node)
        lost++;

      TREE_VEC_ELT (vec, i) = val;
    }
  if (lost)
    return error_mark_node;
  return vec;
}

static 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 (nt == ot)
        continue;
      if (TREE_CODE (nt) != TREE_CODE (ot))
        return 0;
      if (TREE_CODE (nt) == TREE_VEC)
        {
          /* For member templates */
          if (comp_template_args (nt, ot))
            continue;
        }
      else if (TREE_CODE_CLASS (TREE_CODE (ot)) == 't')
        {
          if (comptypes (ot, nt, 1))
            continue;
        }
      else if (cp_tree_equal (ot, nt) > 0)
        continue;
      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, ctx)
     char *name;
     tree parms, arglist;
     tree ctx;
{
  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);

#if 0
#define buflen  sizeof(buf)
#define check   if (bufp >= buf+buflen-1) goto too_long
#define ccat(c) *bufp++=(c); check
#define advance bufp+=strlen(bufp); check
#define cat(s)  strncpy(bufp, s, buf+buflen-bufp-1); advance
#else
#define check
#define ccat(c) obstack_1grow (&scratch_obstack, (c));
#define advance
#define cat(s)  obstack_grow (&scratch_obstack, (s), strlen (s))
#endif

  if (ctx)
    {
      char* s;

      if (TREE_CODE (ctx) == FUNCTION_DECL)
        s = fndecl_as_string(ctx, 0);
      else if (TREE_CODE_CLASS (TREE_CODE (ctx)) == 't')
        s = type_as_string(ctx, 0);
      else
        my_friendly_abort (0);
      cat (s);
      cat ("::");
    }
  cat (name);
  ccat ('<');
  nparms = TREE_VEC_LENGTH (parms);
  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 (arg, 0));
          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 */
            cat (IDENTIFIER_POINTER (DECL_NAME (arg)));
          else
            /* Output the parameter declaration */
            cat (type_as_string (arg, 0));
          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);

#if 0
 too_long:
#endif
  fatal ("out of (preallocated) string space creating template instantiation name");
  /* NOTREACHED */
  return NULL;
}

static tree
classtype_mangled_name (t)
     tree t;
{
  if (CLASSTYPE_TEMPLATE_INFO (t)
      && PRIMARY_TEMPLATE_P (CLASSTYPE_TI_TEMPLATE (t)))
    {
      tree name = DECL_NAME (CLASSTYPE_TI_TEMPLATE (t));
      char *mangled_name = mangle_class_name_for_template
        (IDENTIFIER_POINTER (name),
         DECL_INNERMOST_TEMPLATE_PARMS (CLASSTYPE_TI_TEMPLATE (t)),
         CLASSTYPE_TI_ARGS (t), DECL_CONTEXT (t));
      tree id = get_identifier (mangled_name);
      IDENTIFIER_TEMPLATE (id) = name;
      return id;
    }
  else
    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
    (current_function_decl, 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;
{
  if (fns == NULL_TREE)
    {
      cp_error ("non-template used as template");
      return error_mark_node;
    }

  if (arglist != NULL_TREE && !TREE_PERMANENT (arglist))
    copy_to_permanent (arglist);

  return build_min (TEMPLATE_ID_EXPR,
                    TREE_TYPE (fns) 
                    ? TREE_TYPE (fns) : unknown_type_node, 
                    fns, arglist);  
}


/* 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.
   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 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)
     tree d1, arglist;
     tree in_decl;
     tree context;
{
  tree template = NULL_TREE, parmlist;
  char *mangled_name;
  tree id, t;

  if (TREE_CODE (d1) == IDENTIFIER_NODE)
    {
      if (IDENTIFIER_LOCAL_VALUE (d1) 
          && DECL_TEMPLATE_TEMPLATE_PARM_P (IDENTIFIER_LOCAL_VALUE (d1)))
        template = IDENTIFIER_LOCAL_VALUE (d1);
      else
        {
          template = IDENTIFIER_GLOBAL_VALUE (d1); /* XXX */
          if (! template)
            template = IDENTIFIER_CLASS_VALUE (d1);
        }
    }
  else if (TREE_CODE (d1) == TYPE_DECL && IS_AGGR_TYPE (TREE_TYPE (d1)))
    {
      if (CLASSTYPE_TEMPLATE_INFO (TREE_TYPE (d1)) == NULL_TREE)
        return error_mark_node;
      template = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (d1));
      d1 = DECL_NAME (template);
    }
  else if (TREE_CODE_CLASS (TREE_CODE (d1)) == 't' && IS_AGGR_TYPE (d1))
    {
      template = CLASSTYPE_TI_TEMPLATE (d1);
      d1 = DECL_NAME (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_LOCAL_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)
    return error_mark_node;
  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;

      CLASSTYPE_GOT_SEMICOLON (parm) = 1;
      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);
      CLASSTYPE_TEMPLATE_INFO (parm)
        = perm_tree_cons (template2, arglist2, NULL_TREE);
      TYPE_SIZE (parm) = 0;
      return parm;
    }
  else if (PRIMARY_TEMPLATE_P (template)
           || (TREE_CODE (TYPE_CONTEXT (TREE_TYPE (template))) 
               == FUNCTION_DECL))
    {
      parmlist = DECL_INNERMOST_TEMPLATE_PARMS (template);

      arglist = coerce_template_parms (parmlist, arglist, template,
                                       1, 1);
      if (arglist == error_mark_node)
        return error_mark_node;
      if (uses_template_parms (arglist))
        {
          tree found;
          if (comp_template_args
              (CLASSTYPE_TI_ARGS (TREE_TYPE (template)), arglist))
            found = TREE_TYPE (template);
          else
            {
              for (found = DECL_TEMPLATE_INSTANTIATIONS (template);
                   found; found = TREE_CHAIN (found))
                {
                  if (TI_USES_TEMPLATE_PARMS (found)
                      && comp_template_args (TREE_PURPOSE (found), arglist))
                    break;
                }
              if (found)
                found = TREE_VALUE (found);
            }

          if (found)
            {
              if (can_free (&permanent_obstack, arglist))
                obstack_free (&permanent_obstack, arglist);
              return found;
            }
        }

      mangled_name = mangle_class_name_for_template (IDENTIFIER_POINTER (d1),
                                                     parmlist,
                                                     arglist,
                                                     context);
      id = get_identifier (mangled_name);
      IDENTIFIER_TEMPLATE (id) = d1;

      maybe_push_to_top_level (uses_template_parms (arglist));
      t = xref_tag_from_type (TREE_TYPE (template), id, 1);

      if (context != NULL_TREE)
        {
          /* Set up the context for the type_decl correctly.  Note
             that we must clear DECL_ASSEMBLER_NAME to fool
             build_overload_name into creating a new name.  */
          tree type_decl = TYPE_STUB_DECL (t);

          TYPE_CONTEXT (t) = context;
          DECL_CONTEXT (type_decl) = context;
          DECL_ASSEMBLER_NAME (type_decl) = DECL_NAME (type_decl);
          DECL_ASSEMBLER_NAME (type_decl) = 
            get_identifier (build_overload_name (t, 1, 1));
        }

      pop_from_top_level ();
    }
  else
    {
      tree type_ctx = TYPE_CONTEXT (TREE_TYPE (template));
      tree args = tsubst (CLASSTYPE_TI_ARGS (type_ctx),
                          arglist,
                          TREE_VEC_LENGTH (arglist),
                          in_decl);
      tree ctx = lookup_template_class (type_ctx, args,
                                        in_decl, NULL_TREE);
      id = d1;
      arglist = CLASSTYPE_TI_ARGS (ctx);

      if (TYPE_BEING_DEFINED (ctx) && ctx == current_class_type)
        {
          int save_temp = processing_template_decl;
          processing_template_decl = 0;
          t = xref_tag_from_type (TREE_TYPE (template), id, 0);
          processing_template_decl = save_temp;
        }
      else
        {
          t = lookup_nested_type_by_name (ctx, id);
          my_friendly_assert (t != NULL_TREE, 42);
        }
    }

  /* Seems to be wanted.  */
  CLASSTYPE_GOT_SEMICOLON (t) = 1;

  if (! CLASSTYPE_TEMPLATE_INFO (t))
    {
      arglist = copy_to_permanent (arglist);
      CLASSTYPE_TEMPLATE_INFO (t)
        = perm_tree_cons (template, arglist, NULL_TREE);
      DECL_TEMPLATE_INSTANTIATIONS (template) = perm_tree_cons
        (arglist, t, DECL_TEMPLATE_INSTANTIATIONS (template));
      TI_USES_TEMPLATE_PARMS (DECL_TEMPLATE_INSTANTIATIONS (template))
        = uses_template_parms (arglist);

      SET_CLASSTYPE_IMPLICIT_INSTANTIATION (t);

      /* We need to set this again after CLASSTYPE_TEMPLATE_INFO is set up.  */
      DECL_ASSEMBLER_NAME (TYPE_MAIN_DECL (t)) = id;
      /* if (! uses_template_parms (arglist)) */
        DECL_ASSEMBLER_NAME (TYPE_MAIN_DECL (t)) 
          = get_identifier (build_overload_name (t, 1, 1));

      if (flag_external_templates && ! uses_template_parms (arglist)
          && CLASSTYPE_INTERFACE_KNOWN (TREE_TYPE (template))
          && ! CLASSTYPE_INTERFACE_ONLY (TREE_TYPE (template)))
        add_pending_template (t);
    }

  return t;
}
\f
/* Should be defined in parse.h.  */
extern int yychar;

int
uses_template_parms (t)
     tree t;
{
  if (!t)
    return 0;
  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 uses_template_parms (TREE_TYPE (t));

    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 (uses_template_parms (TREE_VEC_ELT (t, i)))
            return 1;
        return 0;
      }
    case TREE_LIST:
      if (uses_template_parms (TREE_PURPOSE (t))
          || uses_template_parms (TREE_VALUE (t)))
        return 1;
      return uses_template_parms (TREE_CHAIN (t));

      /* constructed type nodes */
    case POINTER_TYPE:
    case REFERENCE_TYPE:
      return uses_template_parms (TREE_TYPE (t));
    case RECORD_TYPE:
      if (TYPE_PTRMEMFUNC_FLAG (t))
        return uses_template_parms (TYPE_PTRMEMFUNC_FN_TYPE (t));
    case UNION_TYPE:
      if (! CLASSTYPE_TEMPLATE_INFO (t))
        return 0;
      return uses_template_parms (TREE_VALUE (CLASSTYPE_TEMPLATE_INFO (t)));
    case FUNCTION_TYPE:
      if (uses_template_parms (TYPE_ARG_TYPES (t)))
        return 1;
      return uses_template_parms (TREE_TYPE (t));
    case ARRAY_TYPE:
      if (uses_template_parms (TYPE_DOMAIN (t)))
        return 1;
      return uses_template_parms (TREE_TYPE (t));
    case OFFSET_TYPE:
      if (uses_template_parms (TYPE_OFFSET_BASETYPE (t)))
        return 1;
      return uses_template_parms (TREE_TYPE (t));
    case METHOD_TYPE:
      if (uses_template_parms (TYPE_METHOD_BASETYPE (t)))
        return 1;
      if (uses_template_parms (TYPE_ARG_TYPES (t)))
        return 1;
      return uses_template_parms (TREE_TYPE (t));

      /* decl nodes */
    case TYPE_DECL:
      return uses_template_parms (TREE_TYPE (t));

    case TEMPLATE_DECL:
      /* A template template parameter is encountered */
      if (DECL_TEMPLATE_TEMPLATE_PARM_P (t))
        /* We are parsing a template declaration */
        return 1;
      /* We are instantiating templates with template template
         parameter */
      return 0;
      
    case CONST_DECL:
      if (uses_template_parms (DECL_INITIAL (t)))
        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)
          && uses_template_parms (DECL_TI_ARGS (t)))
        return 1;
      /* fall through */
    case PARM_DECL:
    check_type_and_context:
      if (uses_template_parms (TREE_TYPE (t)))
        return 1;
      if (DECL_CONTEXT (t) && uses_template_parms (DECL_CONTEXT (t)))
        return 1;
      return 0;

    case CALL_EXPR:
      return uses_template_parms (TREE_TYPE (t));
    case ADDR_EXPR:
      return uses_template_parms (TREE_OPERAND (t, 0));

      /* template parm nodes */
    case TEMPLATE_TYPE_PARM:
    case TEMPLATE_TEMPLATE_PARM:
    case TEMPLATE_CONST_PARM:
      return 1;

      /* simple type nodes */
    case INTEGER_TYPE:
      if (uses_template_parms (TYPE_MIN_VALUE (t)))
        return 1;
      return uses_template_parms (TYPE_MAX_VALUE (t));

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

    case ENUMERAL_TYPE:
      {
        tree v;

        for (v = TYPE_VALUES (t); v != NULL_TREE; v = TREE_CHAIN (v))
          if (uses_template_parms (TREE_VALUE (v)))
            return 1;
      }
      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 SCOPE_REF:
      return uses_template_parms (TREE_OPERAND (t, 0));

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

    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 uses_template_parms (TREE_OPERAND (t, 0));

    default:
      switch (TREE_CODE_CLASS (TREE_CODE (t)))
        {
        case '1':
        case '2':
        case 'e':
        case '<':
          {
            int i;
            for (i = tree_code_length[(int) TREE_CODE (t)]; --i >= 0;)
              if (uses_template_parms (TREE_OPERAND (t, i)))
                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;
    }
}

static struct tinst_level *current_tinst_level = 0;
static struct tinst_level *free_tinst_level = 0;
static int tinst_depth = 0;
extern int max_tinst_depth;
#ifdef GATHER_STATISTICS
int depth_reached = 0;
#endif

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

  if (tinst_depth >= max_tinst_depth)
    {
      struct tinst_level *p = current_tinst_level;
      int line = lineno;
      char *file = input_filename;

      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);

      for (; p; p = p->next)
        {
          cp_error ("  instantiated from `%D'", p->decl);
          lineno = p->line;
          input_filename = p->file;
        }
      error ("  instantiated from here");

      lineno = line;
      input_filename = file;

      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

  return 1;
}

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

  current_tinst_level = old->next;
  old->next = free_tinst_level;
  free_tinst_level = old;
  --tinst_depth;
}

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

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

tree
instantiate_class_template (type)
     tree type;
{
  tree template, template_info, args, pattern, t, *field_chain;

  if (type == error_mark_node)
    return error_mark_node;

  template_info = CLASSTYPE_TEMPLATE_INFO (type);

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

  template = TI_TEMPLATE (template_info);
  my_friendly_assert (TREE_CODE (template) == TEMPLATE_DECL, 279);
  args = TI_ARGS (template_info);

  t = most_specialized_class
    (DECL_TEMPLATE_SPECIALIZATIONS (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;
      return error_mark_node;
    }
  else if (t)
    pattern = TREE_TYPE (t);
  else
    pattern = TREE_TYPE (template);

  if (TYPE_SIZE (pattern) == NULL_TREE)
    return type;

  if (t)
    args = get_class_bindings (TREE_VALUE (t), TREE_PURPOSE (t), args);

  TYPE_BEING_DEFINED (type) = 1;

  if (! push_tinst_level (type))
    return type;

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

  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_GETS_INIT_AGGR (type) = TYPE_GETS_INIT_AGGR (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);

  {
    tree binfo = TYPE_BINFO (type);
    tree pbases = TYPE_BINFO_BASETYPES (pattern);

    if (pbases)
      {
        tree bases;
        int i;
        int len = TREE_VEC_LENGTH (pbases);
        bases = make_tree_vec (len);
        for (i = 0; i < len; ++i)
          {
            tree elt;

            TREE_VEC_ELT (bases, i) = elt
              = tsubst (TREE_VEC_ELT (pbases, i), args,
                        TREE_VEC_LENGTH (args), NULL_TREE);
            BINFO_INHERITANCE_CHAIN (elt) = binfo;

            if (! IS_AGGR_TYPE (TREE_TYPE (elt)))
              cp_error
                ("base type `%T' of `%T' fails to be a struct or class type",
                 TREE_TYPE (elt), type);
            else if (! uses_template_parms (type)
                     && (TYPE_SIZE (complete_type (TREE_TYPE (elt)))
                         == NULL_TREE))
              cp_error ("base class `%T' of `%T' has incomplete type",
                        TREE_TYPE (elt), type);
          }
        /* Don't initialize this until the vector is filled out, or
           lookups will crash.  */
        BINFO_BASETYPES (binfo) = bases;
      }
  }

  CLASSTYPE_LOCAL_TYPEDECLS (type) = CLASSTYPE_LOCAL_TYPEDECLS (pattern);

  field_chain = &TYPE_FIELDS (type);

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

      /* These will add themselves to CLASSTYPE_TAGS for the new type.  */
      if (TREE_CODE (tag) == ENUMERAL_TYPE)
        {
          tree newtag =
            tsubst_enum (tag, args, TREE_VEC_LENGTH (args), field_chain);

          while (*field_chain)
            {
              DECL_FIELD_CONTEXT (*field_chain) = type;
              field_chain = &TREE_CHAIN (*field_chain);
            }
        }
      else
        tsubst (tag, args,
                TREE_VEC_LENGTH (args), NULL_TREE);
    }

  /* Don't replace enum constants here.  */
  for (t = TYPE_FIELDS (pattern); t; t = TREE_CHAIN (t))
    if (TREE_CODE (t) != CONST_DECL)
      {
        tree r = tsubst (t, args,
                         TREE_VEC_LENGTH (args), NULL_TREE);
        if (TREE_CODE (r) == VAR_DECL)
          {
            if (! uses_template_parms (r))
              pending_statics = perm_tree_cons (NULL_TREE, r, pending_statics);
            /* Perhaps I should do more of grokfield here.  */
            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);
          }

        *field_chain = r;
        field_chain = &TREE_CHAIN (r);
      }

  TYPE_METHODS (type) = tsubst_chain (TYPE_METHODS (pattern), args);
  for (t = TYPE_METHODS (type); t; t = TREE_CHAIN (t))
    {
      if (DECL_CONSTRUCTOR_P (t))
        grok_ctor_properties (type, t);
      else if (IDENTIFIER_OPNAME_P (DECL_NAME (t)))
        grok_op_properties (t, DECL_VIRTUAL_P (t), 0);
    }

  DECL_FRIENDLIST (TYPE_MAIN_DECL (type))
    = tsubst (DECL_FRIENDLIST (TYPE_MAIN_DECL (pattern)),
              args, TREE_VEC_LENGTH (args), NULL_TREE);

  {
    tree d = CLASSTYPE_FRIEND_CLASSES (type)
      = tsubst (CLASSTYPE_FRIEND_CLASSES (pattern), args,
                TREE_VEC_LENGTH (args), NULL_TREE);

    /* This does injection for friend classes.  */
    for (; d; d = TREE_CHAIN (d))
      TREE_VALUE (d) = xref_tag_from_type (TREE_VALUE (d), NULL_TREE, 1);

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

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

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

  if (! uses_template_parms (type))
    {
      tree tmp;
      for (tmp = TYPE_FIELDS (type); tmp; tmp = TREE_CHAIN (tmp))
        if (TREE_CODE (tmp) == FIELD_DECL)
          {
            TREE_TYPE (tmp) = complete_type (TREE_TYPE (tmp));
            require_complete_type (tmp);
          }

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

      repo_template_used (type);
      if (at_eof && TYPE_BINFO_VTABLE (type) != NULL_TREE)
        finish_prevtable_vardecl (NULL, TYPE_BINFO_VTABLE (type));
    }
  else
    {
      TYPE_SIZE (type) = integer_zero_node;
      CLASSTYPE_METHOD_VEC (type)
        = finish_struct_methods (type, TYPE_METHODS (type), 1);
    }

  TYPE_BEING_DEFINED (type) = 0;
  popclass (0);

  pop_from_top_level ();
  pop_tinst_level ();

  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));
}

tree 
lookup_nested_type_by_name (ctype, name)
        tree ctype, name;
{
  tree t;

  complete_type (ctype);

  for (t = CLASSTYPE_TAGS (ctype); t; t = TREE_CHAIN (t))
    {
      if (name == TREE_PURPOSE (t)
          /* this catches typedef enum { foo } bar; */
          || name == TYPE_IDENTIFIER (TREE_VALUE (t)))
        return TREE_VALUE (t);
    }
  return NULL_TREE;
}

/* 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;
}

/* Take the tree structure T and replace template parameters used therein
   with the argument vector ARGS.  NARGS is the number of args; should
   be removed.  IN_DECL is an associated decl for diagnostics.

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

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

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

  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)
    type = tsubst (type, args, nargs, in_decl);

  switch (TREE_CODE (t))
    {
    case RECORD_TYPE:
      if (TYPE_PTRMEMFUNC_P (t))
        {
          tree r = build_ptrmemfunc_type
            (tsubst (TYPE_PTRMEMFUNC_FN_TYPE (t), args, nargs, in_decl));
          return cp_build_type_variant (r, TYPE_READONLY (t),
                                        TYPE_VOLATILE (t));
        }

      /* else fall through */
    case UNION_TYPE:
      if (uses_template_parms (t))
        {
          tree argvec = tsubst (CLASSTYPE_TI_ARGS (t), args, nargs, in_decl);
          tree context;
          tree r;

          context = 
            TYPE_CONTEXT (t) 
            ? tsubst (TYPE_CONTEXT (t), args, nargs, in_decl) : NULL_TREE;

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

          return cp_build_type_variant (r, TYPE_READONLY (t),
                                        TYPE_VOLATILE (t));
        }

      /* else fall through */
    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 ENUMERAL_TYPE:
      {
        tree ctx = tsubst (TYPE_CONTEXT (t), args, nargs, in_decl);
        if (ctx == NULL_TREE)
          return t;
        else if (ctx == current_function_decl)
          return lookup_name (TYPE_IDENTIFIER (t), 1);
        else
          return lookup_nested_type_by_name (ctx, TYPE_IDENTIFIER (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 = TREE_OPERAND (TYPE_MAX_VALUE (t), 0);
        max = tsubst_expr (max, args, nargs, in_decl);
        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;
          }

        max = fold (build_binary_op (MINUS_EXPR, max, integer_one_node, 1));
        return build_index_2_type (size_zero_node, max);
      }

    case TEMPLATE_TYPE_PARM:
    case TEMPLATE_TEMPLATE_PARM:
    case TEMPLATE_CONST_PARM:
      {
        int idx;
        int level;

        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_CONST_IDX (t);
            level = TEMPLATE_CONST_LEVEL (t);
          }

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

            if (TREE_CODE (TREE_VEC_ELT (args, 0)) == TREE_VEC)
              {
                if (TREE_VEC_LENGTH (args) >= level - 1)
                  arg = TREE_VEC_ELT
                    (TREE_VEC_ELT (args, level - 1), idx);
              }
            else if (level == 1)
              arg = TREE_VEC_ELT (args, idx);

            if (arg != NULL_TREE)
              {
                if (TREE_CODE (t) == TEMPLATE_TYPE_PARM)
                  return cp_build_type_variant
                    (arg, TYPE_READONLY (arg) || TYPE_READONLY (t),
                     TYPE_VOLATILE (arg) || TYPE_VOLATILE (t));
                else if (TREE_CODE (t) == TEMPLATE_TEMPLATE_PARM)
                  {
                    if (CLASSTYPE_TEMPLATE_INFO (t))
                      {
                        /* We are processing a type constructed from
                           a template template parameter */
                        tree argvec = tsubst (CLASSTYPE_TI_ARGS (t),
                                              args, nargs, in_decl);
                        tree r;

                        /* 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));
                        return cp_build_type_variant (r, TYPE_READONLY (t),
                                                      TYPE_VOLATILE (t));
                      }
                    else
                      /* We are processing a template argument list.  */ 
                      return arg;
                  }
                else
                  return arg;
              }
          }

        /* If we get here, we must have been looking at a parm for a
           more deeply nested template.  */
        my_friendly_assert((TREE_CODE (t) == TEMPLATE_CONST_PARM 
                            && TEMPLATE_CONST_LEVEL (t) > 1) 
                           || (TREE_CODE (t) == TEMPLATE_TYPE_PARM
                               && TEMPLATE_TYPE_LEVEL (t) > 1)
                           || (TREE_CODE (t) == TEMPLATE_TEMPLATE_PARM
                               && TEMPLATE_TYPE_LEVEL (t) > 1),
                           0);
        return t;
      }

    case TEMPLATE_DECL:
      {
        /* We can get here when processing a member template function
           of a template class.  */
        tree tmpl;
        tree decl = DECL_TEMPLATE_RESULT (t);
        tree new_decl;
        tree parms;
        tree spec;

        /* We might already have an instance of this template. */
        spec = retrieve_specialization (t, args);
        if (spec != NULL_TREE)
          return spec;

        /* 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.  */
        tmpl = copy_node (t);
        copy_lang_decl (tmpl);
        my_friendly_assert (DECL_LANG_SPECIFIC (tmpl) != 0, 0);
        DECL_CHAIN (tmpl) = NULL_TREE;
        TREE_CHAIN (tmpl) = NULL_TREE;
        DECL_TEMPLATE_INFO (tmpl) = build_tree_list (t, args);
        new_decl = tsubst (decl, args, nargs, in_decl);
        DECL_RESULT (tmpl) = new_decl;
        DECL_TI_TEMPLATE (new_decl) = tmpl;
        TREE_TYPE (tmpl) = TREE_TYPE (new_decl);
        DECL_TEMPLATE_INSTANTIATIONS (tmpl) = NULL_TREE;
        SET_DECL_IMPLICIT_INSTANTIATION (tmpl);

        /* 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 (tmpl)
          = copy_node (DECL_TEMPLATE_PARMS (tmpl));
        for (parms = DECL_TEMPLATE_PARMS (tmpl);
             TREE_CHAIN (parms) != NULL_TREE;
             parms = TREE_CHAIN (parms))
          TREE_CHAIN (parms) = copy_node (TREE_CHAIN (parms));

        /* What should we do with the specializations of this member
           template?  Are they specializations of this new template,
           or instantiations of the templates they previously were?
           this new template?  And where should their
           DECL_TI_TEMPLATES point?  */ 
        DECL_TEMPLATE_SPECIALIZATIONS (tmpl) = NULL_TREE;
        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;

            spec_args = tsubst (DECL_TI_ARGS (fn), args, nargs,
                                in_decl); 
            new_fn = tsubst (DECL_RESULT (fn), args, nargs,
                             in_decl); 
            DECL_TEMPLATE_SPECIALIZATIONS (tmpl) = 
              perm_tree_cons (spec_args, new_fn, 
                              DECL_TEMPLATE_SPECIALIZATIONS (tmpl));
          }

        /* Record this partial instantiation.  */
        register_specialization (tmpl, t, args);

        return tmpl;
      }

    case FUNCTION_DECL:
      {
        tree r = NULL_TREE;
        tree ctx;

        int member;

        if (DECL_CONTEXT (t) != NULL_TREE
            && TREE_CODE_CLASS (TREE_CODE (DECL_CONTEXT (t))) == 't')
          {
            if (DECL_NAME (t) == constructor_name (DECL_CONTEXT (t)))
              member = 2;
            else
              member = 1;
            ctx = tsubst (DECL_CLASS_CONTEXT (t), args, nargs, t);
            type = tsubst (type, args, nargs, in_decl);
          }
        else
          {
            member = 0;
            ctx = NULL_TREE;
            type = tsubst (type, args, nargs, in_decl);
          }

        /* Do we already have this instantiation?  */
        if (DECL_TEMPLATE_INFO (t) != NULL_TREE)
          {
            tree tmpl = DECL_TI_TEMPLATE (t);
            tree spec = retrieve_specialization (tmpl, args);

            if (spec)
              return spec;
          }

        /* 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 (DECL_CONTEXT (t), args, nargs, t);
        DECL_CLASS_CONTEXT (r) = ctx;

        if (member && !strncmp (OPERATOR_TYPENAME_FORMAT,
                                IDENTIFIER_POINTER (DECL_NAME (r)),
                                sizeof (OPERATOR_TYPENAME_FORMAT) - 1))
          {
            /* 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));
          }

        if (DESTRUCTOR_NAME_P (DECL_ASSEMBLER_NAME (t)))
          {
            char *buf, *dbuf = build_overload_name (ctx, 1, 1);
            int len = sizeof (DESTRUCTOR_DECL_PREFIX) - 1;
            buf = (char *) alloca (strlen (dbuf)
                                   + sizeof (DESTRUCTOR_DECL_PREFIX));
            bcopy (DESTRUCTOR_DECL_PREFIX, buf, len);
            buf[len] = '\0';
            strcat (buf, dbuf);
            DECL_ASSEMBLER_NAME (r) = get_identifier (buf);
          }
        else 
          {
            /* Instantiations of template functions must be mangled
               specially, in order to conform to 14.5.5.1
               [temp.over.link].  We use in_decl below rather than
               DECL_TI_TEMPLATE (r) because the latter is set to
               NULL_TREE in instantiate_decl.  */
            tree tmpl;
            tree arg_types;

            if (DECL_TEMPLATE_INFO (r))
              tmpl = DECL_TI_TEMPLATE (r);
            else
              tmpl = in_decl;

            /* tmpl will be NULL if this is a specialization of a
               member template of a template class.  */
            if (name_mangling_version < 1
                || tmpl == NULL_TREE
                || (member && !is_member_template (tmpl)
                    && !DECL_TEMPLATE_INFO (tmpl)))
              {
                arg_types = TYPE_ARG_TYPES (type);
                if (member && TREE_CODE (type) == FUNCTION_TYPE)
                  arg_types = hash_tree_chain 
                    (build_pointer_type (DECL_CONTEXT (r)),
                     arg_types); 
                
                DECL_ASSEMBLER_NAME (r) 
                  = build_decl_overload (DECL_NAME (r), arg_types,
                                         member);
              }
            else
              {
                /* We pass the outermost template parameters to
                   build_template_decl_overload since the innermost
                   template parameters are still just template
                   parameters; there are no corresponding subsitution
                   arguments.  */
                /* FIXME The messed up thing here is that we get here with
                   full args and only one level of parms.  This is necessary
                   because when we partially instantiate a member template,
                   even though there's really only one level of parms left
                   we re-use the parms from the original template, which
                   have level 2.  When this is fixed we can remove the
                   add_to_template_args from instantiate_template.  */
                tree tparms;
                tree targs;

                if (!DECL_TEMPLATE_SPECIALIZATION (tmpl)) 
                  {
                    tparms = DECL_TEMPLATE_PARMS (tmpl);

                    while (tparms && TREE_CHAIN (tparms) != NULL_TREE)
                      tparms = TREE_CHAIN (tparms);
                    
                    targs = 
                      (TREE_CODE (TREE_VEC_ELT (args, 0)) == TREE_VEC 
                       ? TREE_VEC_ELT (args, TREE_VEC_LENGTH (args) - 1)
                       : args); 
                  }
                else
                  {
                    /* If the template is a specialization, then it is
                       a member template specialization.  We have
                       something like:

                       template <class T> struct S {
                         template <int i> void f();
                         template <> void f<7>();
                       };

                       and now we are forming S<double>::f<7>.
                       Therefore, the template parameters of interest
                       are those that are specialized by the template
                       (i.e., the int), not those we are using to
                       instantiate the template, i.e. the double.  */
                    tparms = DECL_TEMPLATE_PARMS (DECL_TI_TEMPLATE (tmpl));
                    targs = DECL_TI_ARGS (tmpl);
                  }
                    
                my_friendly_assert (tparms != NULL_TREE
                                    && TREE_CODE (tparms) == TREE_LIST,
                                    0);
                tparms = TREE_VALUE (tparms);
                 
                arg_types = TYPE_ARG_TYPES (TREE_TYPE (tmpl));
                if (member && TREE_CODE (type) == FUNCTION_TYPE)
                  arg_types = hash_tree_chain 
                    (build_pointer_type (DECL_CONTEXT (r)),
                     arg_types); 

                DECL_ASSEMBLER_NAME (r)
                  = build_template_decl_overload 
                  (DECL_NAME (r), arg_types, 
                   TREE_TYPE (TREE_TYPE (tmpl)),
                   tparms, targs, member);
              }
          }
        DECL_RTL (r) = 0;
        make_decl_rtl (r, NULL_PTR, 1);

        DECL_ARGUMENTS (r) = tsubst (DECL_ARGUMENTS (t), args, nargs, t);
        DECL_MAIN_VARIANT (r) = r;
        DECL_RESULT (r) = NULL_TREE;
        DECL_INITIAL (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_CHAIN (r) = NULL_TREE;

        if (IDENTIFIER_OPNAME_P (DECL_NAME (r)))
          grok_op_properties (r, DECL_VIRTUAL_P (r), DECL_FRIEND_P (r));

        /* Look for matching decls for the moment.  */
        if (! member && ! flag_ansi_overloading)
          {
            tree decls = lookup_name_nonclass (DECL_NAME (t));
            tree d = NULL_TREE;
    
            if (decls == NULL_TREE)
              /* no match */;
            else if (is_overloaded_fn (decls))
              for (decls = get_first_fn (decls); decls;
                   decls = DECL_CHAIN (decls))
                {
                  if (TREE_CODE (decls) == FUNCTION_DECL
                      && TREE_TYPE (decls) == type)
                    {
                      d = decls;
                      break;
                    }
                }

            if (d)
              {
                int dcl_only = ! DECL_INITIAL (d);
                if (dcl_only)
                  DECL_INITIAL (r) = error_mark_node;
                duplicate_decls (r, d);
                r = d;
                if (dcl_only)
                  DECL_INITIAL (r) = 0;
              }
          }

        if (DECL_TEMPLATE_INFO (t) != NULL_TREE)
          {
            tree tmpl = DECL_TI_TEMPLATE (t);
            tree argvec = tsubst (DECL_TI_ARGS (t), args, nargs, in_decl);

            if (DECL_TEMPLATE_INFO (tmpl) && DECL_TI_ARGS (tmpl))
              {
                if (!DECL_TEMPLATE_SPECIALIZATION (tmpl))
                  argvec = add_to_template_args (DECL_TI_ARGS (tmpl), argvec);
                else
                  /* In this case, we are instantiating a
                     specialization.  The innermost template args are
                     already given by the specialization.  */
                  argvec = add_to_template_args (argvec, DECL_TI_ARGS (tmpl));
              }

            DECL_TEMPLATE_INFO (r) = perm_tree_cons (tmpl, argvec, NULL_TREE);

            /* If we're not using ANSI overloading, then we might have
               called duplicate_decls above, and gotten back an
               preexisting version of this function.  We treat such a
               function as a specialization.  Otherwise, we cleared
               both TREE_STATIC and DECL_TEMPLATE_SPECIALIZATION, so
               this condition will be false.  */
            if (TREE_STATIC (r) || DECL_TEMPLATE_SPECIALIZATION (r))
              SET_DECL_TEMPLATE_SPECIALIZATION (r);
            else
              SET_DECL_IMPLICIT_INSTANTIATION (r);

            register_specialization (r, tmpl, argvec);
          }

        /* 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
            && IDENTIFIER_GLOBAL_VALUE (DECL_ASSEMBLER_NAME (r)) == NULL_TREE)
          IDENTIFIER_GLOBAL_VALUE (DECL_ASSEMBLER_NAME (r)) = r;

        return r;
      }

    case PARM_DECL:
      {
        tree r = copy_node (t);
        TREE_TYPE (r) = type;
        DECL_INITIAL (r) = TREE_TYPE (r);
        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, nargs, TREE_CHAIN (t));
        return r;
      }

    case FIELD_DECL:
      {
        tree r = copy_node (t);
        TREE_TYPE (r) = type;
        copy_lang_decl (r);
#if 0
        DECL_FIELD_CONTEXT (r) = tsubst (DECL_FIELD_CONTEXT (t), args, nargs, in_decl);
#endif
        DECL_INITIAL (r) = tsubst_expr (DECL_INITIAL (t), args, nargs, in_decl);
        TREE_CHAIN (r) = NULL_TREE;
        return r;
      }

    case USING_DECL:
      {
        tree r = copy_node (t);
        DECL_INITIAL (r)
          = tsubst_copy (DECL_INITIAL (t), args, nargs, in_decl);
        TREE_CHAIN (r) = NULL_TREE;
        return r;
      }

    case VAR_DECL:
      {
        tree r;
        tree ctx = tsubst_copy (DECL_CONTEXT (t), args, nargs, in_decl);

        /* Do we already have this instantiation?  */
        if (DECL_LANG_SPECIFIC (t) && DECL_TEMPLATE_INFO (t))
          {
            tree tmpl = DECL_TI_TEMPLATE (t);
            tree decls = DECL_TEMPLATE_INSTANTIATIONS (tmpl);

            for (; decls; decls = TREE_CHAIN (decls))
              if (DECL_CONTEXT (TREE_VALUE (decls)) == ctx)
                return TREE_VALUE (decls);
          }

        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;

        if (DECL_LANG_SPECIFIC (r))
          {
            copy_lang_decl (r);
            DECL_CLASS_CONTEXT (r) = DECL_CONTEXT (r);
          }

        if (DECL_LANG_SPECIFIC (t) && DECL_TEMPLATE_INFO (t))
          {
            tree tmpl = DECL_TI_TEMPLATE (t);
            tree *declsp = &DECL_TEMPLATE_INSTANTIATIONS (tmpl);
            tree argvec = tsubst (DECL_TI_ARGS (t), args, nargs, in_decl);

            DECL_TEMPLATE_INFO (r) = perm_tree_cons (tmpl, argvec, NULL_TREE);
            *declsp = perm_tree_cons (argvec, r, *declsp);
            SET_DECL_IMPLICIT_INSTANTIATION (r);
          }
        TREE_CHAIN (r) = NULL_TREE;
        return r;
      }

    case TYPE_DECL:
      if (t == TYPE_NAME (TREE_TYPE (t)))
        return TYPE_NAME (type);

      {
        tree r = copy_node (t);
        TREE_TYPE (r) = type;
        DECL_CONTEXT (r) = current_class_type;
        TREE_CHAIN (r) = NULL_TREE;
        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, nargs, in_decl);
        value = TREE_VALUE (t);
        if (value)
          value = tsubst (value, args, nargs, in_decl);
        chain = TREE_CHAIN (t);
        if (chain && chain != void_type_node)
          chain = tsubst (chain, args, nargs, in_decl);
        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.  */

          t = copy_node (t);

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

          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.  */
      {
        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++)
          {
            elts[i] = maybe_fold_nontype_arg
              (tsubst_expr (TREE_VEC_ELT (t, i), args, nargs, in_decl));

            if (elts[i] != TREE_VEC_ELT (t, i))
              need_new = 1;
          }

        if (!need_new)
          return t;

        t = make_tree_vec (len);
        for (i = 0; i < len; i++)
          TREE_VEC_ELT (t, i) = elts[i];
        
        return t;
      }
    case POINTER_TYPE:
    case REFERENCE_TYPE:
      {
        tree r;
        enum tree_code code;

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

        code = TREE_CODE (t);
        if (TREE_CODE (type) == REFERENCE_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 (last_line != lineno ||
                last_file != input_filename)
              {
                cp_error ("cannot form type %s to reference type %T during template instantiation",
                          (code == POINTER_TYPE) ? "pointer" : "reference",
                          type);
                last_line = lineno;
                last_file = input_filename;
              }

            /* Use the underlying type in an attempt at error
               recovery; maybe the user meant vector<int> and wrote
               vector<int&>, or some such.  */
            if (code == REFERENCE_TYPE)
              r = type;
            else
              r = build_pointer_type (TREE_TYPE (type));
          }
        else if (code == POINTER_TYPE)
          r = build_pointer_type (type);
        else
          r = build_reference_type (type);
        r = cp_build_type_variant (r, TYPE_READONLY (t), TYPE_VOLATILE (t));

        /* Will this ever be needed for TYPE_..._TO values?  */
        layout_type (r);
        return r;
      }
    case OFFSET_TYPE:
      return build_offset_type
        (tsubst (TYPE_OFFSET_BASETYPE (t), args, nargs, in_decl), type);
    case FUNCTION_TYPE:
    case METHOD_TYPE:
      {
        tree values = TYPE_ARG_TYPES (t);
        tree context = TYPE_CONTEXT (t);
        tree raises = TYPE_RAISES_EXCEPTIONS (t);
        tree fntype;

        /* Don't bother recursing if we know it won't change anything.  */
        if (values != void_list_node)
          {
            /* This should probably be rewritten to use hash_tree_cons for
               the memory savings.  */
            tree first = NULL_TREE;
            tree last = NULL_TREE;

            for (; values && values != void_list_node;
                 values = TREE_CHAIN (values))
              {
                tree value = TYPE_MAIN_VARIANT (type_decays_to
                  (tsubst (TREE_VALUE (values), args, nargs, in_decl)));
                /* Don't instantiate default args unless they are used.
                   Handle it in build_over_call instead.  */
                tree purpose = TREE_PURPOSE (values);
                tree x = build_tree_list (purpose, value);

                if (first)
                  TREE_CHAIN (last) = x;
                else
                  first = x;
                last = x;
              }

            if (values == void_list_node)
              TREE_CHAIN (last) = void_list_node;

            values = first;
          }
        if (context)
          context = tsubst (context, args, nargs, in_decl);
        /* Could also optimize cases where return value and
           values have common elements (e.g., T min(const &T, const T&).  */

        /* If the above parameters haven't changed, just return the type.  */
        if (type == TREE_TYPE (t)
            && values == TYPE_VALUES (t)
            && context == TYPE_CONTEXT (t))
          return t;

        /* Construct a new type node and return it.  */
        if (TREE_CODE (t) == FUNCTION_TYPE
            && context == NULL_TREE)
          {
            fntype = build_function_type (type, values);
          }
        else if (context == NULL_TREE)
          {
            tree base = tsubst (TREE_TYPE (TREE_VALUE (TYPE_ARG_TYPES (t))),
                                args, nargs, in_decl);
            fntype = build_cplus_method_type (base, type,
                                              TREE_CHAIN (values));
          }
        else
          {
            fntype = make_node (TREE_CODE (t));
            TREE_TYPE (fntype) = type;
            TYPE_CONTEXT (fntype) = context;
            TYPE_VALUES (fntype) = values;
            TYPE_SIZE (fntype) = TYPE_SIZE (t);
            TYPE_ALIGN (fntype) = TYPE_ALIGN (t);
            TYPE_MODE (fntype) = TYPE_MODE (t);
            if (TYPE_METHOD_BASETYPE (t))
              TYPE_METHOD_BASETYPE (fntype) = tsubst (TYPE_METHOD_BASETYPE (t),
                                                      args, nargs, in_decl);
            /* Need to generate hash value.  */
            my_friendly_abort (84);
          }
        fntype = build_type_variant (fntype,
                                     TYPE_READONLY (t),
                                     TYPE_VOLATILE (t));
        if (raises)
          {
            raises = tsubst (raises, args, nargs, in_decl);
            fntype = build_exception_variant (fntype, raises);
          }
        return fntype;
      }
    case ARRAY_TYPE:
      {
        tree domain = tsubst (TYPE_DOMAIN (t), args, nargs, in_decl);
        tree r;
        if (type == TREE_TYPE (t) && domain == TYPE_DOMAIN (t))
          return t;
        r = build_cplus_array_type (type, domain);
        return r;
      }

    case PLUS_EXPR:
    case MINUS_EXPR:
      return fold (build (TREE_CODE (t), TREE_TYPE (t),
                          tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl),
                          tsubst (TREE_OPERAND (t, 1), args, nargs, in_decl)));

    case NEGATE_EXPR:
    case NOP_EXPR:
      return fold (build1 (TREE_CODE (t), TREE_TYPE (t),
                           tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl)));

    case TYPENAME_TYPE:
      {
        tree ctx = tsubst (TYPE_CONTEXT (t), args, nargs, in_decl);
        tree f = make_typename_type (ctx, TYPE_IDENTIFIER (t));
        return cp_build_type_variant
          (f, TYPE_READONLY (f) || TYPE_READONLY (t),
           TYPE_VOLATILE (f) || TYPE_VOLATILE (t));
      }

    case INDIRECT_REF:
      return make_pointer_declarator
        (type, tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl));
      
    case ADDR_EXPR:
      return make_reference_declarator
        (type, tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl));

    case ARRAY_REF:
      return build_parse_node
        (ARRAY_REF, tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst_expr (TREE_OPERAND (t, 1), args, nargs, in_decl));

    case CALL_EXPR:
      return make_call_declarator
        (tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst (TREE_OPERAND (t, 1), args, nargs, in_decl),
         TREE_OPERAND (t, 2),
         tsubst (TREE_TYPE (t), args, nargs, in_decl));

    case SCOPE_REF:
      return build_parse_node
        (TREE_CODE (t), tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst (TREE_OPERAND (t, 1), args, nargs, in_decl));

    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, nargs, in_decl)
     tree t, args;
     int nargs;
     tree in_decl;
{
  enum tree_code code;

  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);

    case CONST_DECL:
    case FIELD_DECL:
      if (DECL_CONTEXT (t))
        {
          tree ctx = tsubst (DECL_CONTEXT (t), args, nargs, in_decl);
          if (ctx == current_function_decl)
            return lookup_name (DECL_NAME (t), 0);
          else 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, nargs, in_decl);
      mark_used (t);
      return t;

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

#if 0
    case IDENTIFIER_NODE:
      return do_identifier (t, 0);
#endif
      
    case CAST_EXPR:
    case REINTERPRET_CAST_EXPR:
    case CONST_CAST_EXPR:
    case STATIC_CAST_EXPR:
    case DYNAMIC_CAST_EXPR:
      return build1
        (code, tsubst (TREE_TYPE (t), args, nargs, in_decl),
         tsubst_copy (TREE_OPERAND (t, 0), args, nargs, 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, nargs, 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, nargs, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, nargs, in_decl));

    case CALL_EXPR:
      {
        tree fn = TREE_OPERAND (t, 0);
        if (really_overloaded_fn (fn))
          fn = tsubst_copy (get_first_fn (fn), args, nargs, in_decl);
        else
          fn = tsubst_copy (fn, args, nargs, in_decl);
        return build_nt
          (code, fn, tsubst_copy (TREE_OPERAND (t, 1), args, nargs, 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, nargs, in_decl);
            name = build1 (BIT_NOT_EXPR, NULL_TREE, TYPE_MAIN_VARIANT (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, nargs, in_decl);
            name = TREE_OPERAND (name, 1);
            name = tsubst_copy (TREE_OPERAND (name, 0), args, nargs, in_decl);
            name = build1 (BIT_NOT_EXPR, NULL_TREE, TYPE_MAIN_VARIANT (name));
            name = build_nt (SCOPE_REF, base, name);
          }
        else
          name = tsubst_copy (TREE_OPERAND (t, 0), args, nargs, in_decl);
        return build_nt
          (code, name, tsubst_copy (TREE_OPERAND (t, 1), args, nargs, in_decl),
           tsubst_copy (TREE_OPERAND (t, 2), args, nargs, in_decl),
           NULL_TREE);
      }

    case BIND_EXPR:
    case COND_EXPR:
    case MODOP_EXPR:
      {
        tree r = build_nt
          (code, tsubst_copy (TREE_OPERAND (t, 0), args, nargs, in_decl),
           tsubst_copy (TREE_OPERAND (t, 1), args, nargs, in_decl),
           tsubst_copy (TREE_OPERAND (t, 2), args, nargs, 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_exp = expand_start_stmt_expr();
            tsubst_expr (TREE_OPERAND (r, 1), args, nargs, in_decl);
            rtl_exp = expand_end_stmt_expr (rtl_exp);
            TREE_SIDE_EFFECTS (rtl_exp) = 1;
            return build (BIND_EXPR, TREE_TYPE (rtl_exp), 
                          NULL_TREE, rtl_exp, TREE_OPERAND (r, 2));
          }

        return r;
      }

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

    case DELETE_EXPR:
      {
        tree r = build_nt
        (code, tsubst_copy (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, nargs, 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, nargs, 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, nargs, 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, nargs, in_decl);
        value = TREE_VALUE (t);
        if (value)
          value = tsubst_copy (value, args, nargs, in_decl);
        chain = TREE_CHAIN (t);
        if (chain && chain != void_type_node)
          chain = tsubst_copy (chain, args, nargs, 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_CONST_PARM:
    case POINTER_TYPE:
    case REFERENCE_TYPE:
    case OFFSET_TYPE:
    case FUNCTION_TYPE:
    case METHOD_TYPE:
    case ARRAY_TYPE:
    case TYPENAME_TYPE:
      return tsubst (t, args, nargs, in_decl);

    case IDENTIFIER_NODE:
      if (IDENTIFIER_TYPENAME_P (t))
        return build_typename_overload
          (tsubst (TREE_TYPE (t), args, nargs, in_decl));
      else
        return t;

    case CONSTRUCTOR:
      return build
        (CONSTRUCTOR, tsubst (TREE_TYPE (t), args, nargs, in_decl), NULL_TREE,
         tsubst_copy (CONSTRUCTOR_ELTS (t), args, nargs, in_decl));

    default:
      return t;
    }
}

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

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

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

  switch (TREE_CODE (t))
    {
    case RETURN_STMT:
      lineno = TREE_COMPLEXITY (t);
      emit_line_note (input_filename, lineno);
      c_expand_return
        (tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl));
      finish_stmt ();
      break;

    case EXPR_STMT:
      lineno = TREE_COMPLEXITY (t);
      emit_line_note (input_filename, lineno);
      t = tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl);
      /* Do default conversion if safe and possibly important,
         in case within ({...}).  */
      if ((TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE && lvalue_p (t))
          || TREE_CODE (TREE_TYPE (t)) == FUNCTION_TYPE)
        t = default_conversion (t);
      cplus_expand_expr_stmt (t);
      clear_momentary ();
      finish_stmt ();
      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, nargs, in_decl),
           tsubst (TREE_OPERAND (t, 1), args, nargs, in_decl),
           TREE_OPERAND (t, 2) != 0);
        init = tsubst_expr (TREE_OPERAND (t, 2), args, nargs, in_decl);
        cp_finish_decl
          (dcl, init, NULL_TREE, 1, /*init ? LOOKUP_ONLYCONVERTING :*/ 0);
        resume_momentary (i);
        return dcl;
      }

    case FOR_STMT:
      {
        tree tmp;
        int init_scope = (flag_new_for_scope > 0 && TREE_OPERAND (t, 0)
                          && TREE_CODE (TREE_OPERAND (t, 0)) == DECL_STMT);
        int cond_scope = (TREE_OPERAND (t, 1)
                          && TREE_CODE (TREE_OPERAND (t, 1)) == DECL_STMT);

        lineno = TREE_COMPLEXITY (t);
        emit_line_note (input_filename, lineno);
        if (init_scope)
          do_pushlevel ();
        for (tmp = TREE_OPERAND (t, 0); tmp; tmp = TREE_CHAIN (tmp))
          tsubst_expr (tmp, args, nargs, in_decl);
        emit_nop ();
        emit_line_note (input_filename, lineno);
        expand_start_loop_continue_elsewhere (1); 

        if (cond_scope)
          do_pushlevel ();
        tmp = tsubst_expr (TREE_OPERAND (t, 1), args, nargs, in_decl);
        emit_line_note (input_filename, lineno);
        if (tmp)
          expand_exit_loop_if_false (0, condition_conversion (tmp));

        if (! cond_scope)
          do_pushlevel ();
        tsubst_expr (TREE_OPERAND (t, 3), args, nargs, in_decl);
        do_poplevel ();

        emit_line_note (input_filename, lineno);
        expand_loop_continue_here ();
        tmp = tsubst_expr (TREE_OPERAND (t, 2), args, nargs, in_decl);
        if (tmp)
          cplus_expand_expr_stmt (tmp);

        expand_end_loop ();
        if (init_scope)
          do_poplevel ();
        finish_stmt ();
      }
      break;

    case WHILE_STMT:
      {
        tree cond;

        lineno = TREE_COMPLEXITY (t);
        emit_nop ();
        emit_line_note (input_filename, lineno);
        expand_start_loop (1); 

        cond = TREE_OPERAND (t, 0);
        if (TREE_CODE (cond) == DECL_STMT)
          do_pushlevel ();
        cond = tsubst_expr (cond, args, nargs, in_decl);
        emit_line_note (input_filename, lineno);
        expand_exit_loop_if_false (0, condition_conversion (cond));

        if (TREE_CODE (TREE_OPERAND (t, 0)) != DECL_STMT)
          do_pushlevel ();
        tsubst_expr (TREE_OPERAND (t, 1), args, nargs, in_decl);
        do_poplevel ();

        expand_end_loop ();
        finish_stmt ();
      }
      break;

    case DO_STMT:
      {
        tree cond;

        lineno = TREE_COMPLEXITY (t);
        emit_nop ();
        emit_line_note (input_filename, lineno);
        expand_start_loop_continue_elsewhere (1); 

        tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl);
        expand_loop_continue_here ();

        cond = tsubst_expr (TREE_OPERAND (t, 1), args, nargs, in_decl);
        emit_line_note (input_filename, lineno);
        expand_exit_loop_if_false (0, condition_conversion (cond));
        expand_end_loop ();

        clear_momentary ();
        finish_stmt ();
      }
      break;

    case IF_STMT:
      {
        tree tmp;
        int cond_scope = (TREE_CODE (TREE_OPERAND (t, 0)) == DECL_STMT);

        lineno = TREE_COMPLEXITY (t);
        if (cond_scope)
          do_pushlevel ();
        tmp = tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl);
        emit_line_note (input_filename, lineno);
        expand_start_cond (condition_conversion (tmp), 0);
        
        if (tmp = TREE_OPERAND (t, 1), tmp)
          tsubst_expr (tmp, args, nargs, in_decl);

        if (tmp = TREE_OPERAND (t, 2), tmp)
          {
            expand_start_else ();
            tsubst_expr (tmp, args, nargs, in_decl);
          }

        expand_end_cond ();

        if (cond_scope)
          do_poplevel ();

        finish_stmt ();
      }
      break;

    case COMPOUND_STMT:
      {
        tree substmt = TREE_OPERAND (t, 0);

        lineno = TREE_COMPLEXITY (t);

        if (COMPOUND_STMT_NO_SCOPE (t) == 0)
          do_pushlevel ();

        for (; substmt; substmt = TREE_CHAIN (substmt))
          tsubst_expr (substmt, args, nargs, in_decl);

        if (COMPOUND_STMT_NO_SCOPE (t) == 0)
          do_poplevel ();
      }
      break;

    case BREAK_STMT:
      lineno = TREE_COMPLEXITY (t);
      emit_line_note (input_filename, lineno);
      if (! expand_exit_something ())
        error ("break statement not within loop or switch");
      break;

    case CONTINUE_STMT:
      lineno = TREE_COMPLEXITY (t);
      emit_line_note (input_filename, lineno);
      if (! expand_continue_loop (0))
        error ("continue statement not within a loop");
      break;

    case SWITCH_STMT:
      {
        tree val, tmp;
        int cond_scope = (TREE_CODE (TREE_OPERAND (t, 0)) == DECL_STMT);

        lineno = TREE_COMPLEXITY (t);
        if (cond_scope)
          do_pushlevel ();
        val = tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl);
        emit_line_note (input_filename, lineno);
        c_expand_start_case (val);
        push_switch ();
        
        if (tmp = TREE_OPERAND (t, 1), tmp)
          tsubst_expr (tmp, args, nargs, in_decl);

        expand_end_case (val);
        pop_switch ();

        if (cond_scope)
          do_poplevel ();

        finish_stmt ();
      }
      break;

    case CASE_LABEL:
      do_case (tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl),
               tsubst_expr (TREE_OPERAND (t, 1), args, nargs, 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);
      emit_line_note (input_filename, lineno);
      if (TREE_CODE (TREE_OPERAND (t, 0)) == IDENTIFIER_NODE)
        {
          tree decl = lookup_label (TREE_OPERAND (t, 0));
          TREE_USED (decl) = 1;
          expand_goto (decl);
        }
      else
        expand_computed_goto
          (tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl));
      break;

    case TRY_BLOCK:
      lineno = TREE_COMPLEXITY (t);
      emit_line_note (input_filename, lineno);
      expand_start_try_stmts ();
      tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl);
      expand_start_all_catch ();
      {
        tree handler = TREE_OPERAND (t, 1);
        for (; handler; handler = TREE_CHAIN (handler))
          tsubst_expr (handler, args, nargs, in_decl);
      }
      expand_end_all_catch ();
      break;

    case HANDLER:
      lineno = TREE_COMPLEXITY (t);
      do_pushlevel ();
      if (TREE_OPERAND (t, 0))
        {
          tree d = TREE_OPERAND (t, 0);
          expand_start_catch_block
            (tsubst (TREE_OPERAND (d, 1), args, nargs, in_decl),
             tsubst (TREE_OPERAND (d, 0), args, nargs, in_decl));
        }
      else
        expand_start_catch_block (NULL_TREE, NULL_TREE);
      tsubst_expr (TREE_OPERAND (t, 1), args, nargs, in_decl);
      expand_end_catch_block ();
      do_poplevel ();
      break;

    case TAG_DEFN:
      lineno = TREE_COMPLEXITY (t);
      t = TREE_TYPE (t);
      if (TREE_CODE (t) == ENUMERAL_TYPE)
        tsubst_enum (t, args, nargs, NULL);
      break;

    default:
      return build_expr_from_tree (tsubst_copy (t, args, nargs, in_decl));
    }
  return NULL_TREE;
}

tree
instantiate_template (tmpl, targ_ptr)
     tree tmpl, targ_ptr;
{
  tree fndecl;
  int i, len;
  struct obstack *old_fmp_obstack;
  extern struct obstack *function_maybepermanent_obstack;

  my_friendly_assert (TREE_CODE (tmpl) == TEMPLATE_DECL, 283);

  if (DECL_FUNCTION_TEMPLATE_P (tmpl))
    {
      /* Check to see if we already have this specialization.  */
      tree spec = retrieve_specialization (tmpl, targ_ptr);
      
      if (spec != NULL_TREE)
        return spec;
    }

  push_obstacks (&permanent_obstack, &permanent_obstack);
  old_fmp_obstack = function_maybepermanent_obstack;
  function_maybepermanent_obstack = &permanent_obstack;

  len = DECL_NTPARMS (tmpl);

  i = len;
  while (i--)
    {
      tree t = TREE_VEC_ELT (targ_ptr, 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'", tmpl);
              fndecl = error_mark_node;
              goto out;
            }
        }
      TREE_VEC_ELT (targ_ptr, i) = copy_to_permanent (t);
    }
  targ_ptr = copy_to_permanent (targ_ptr);

  if (DECL_TEMPLATE_INFO (tmpl) && DECL_TI_ARGS (tmpl))
    targ_ptr = add_to_template_args (DECL_TI_ARGS (tmpl), targ_ptr);

  /* substitute template parameters */
  fndecl = tsubst (DECL_RESULT (tmpl), targ_ptr, len, 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);
}


/* Like type_unification but designed specially to handle conversion
   operators.  The EXTRA_FN_ARG, if any, is the type of an additional
   parameter to be added to the beginning of FN's parameter list.  */

int
fn_type_unification (fn, explicit_targs, targs, args, return_type,
                     strict, extra_fn_arg)
     tree fn, explicit_targs, targs, args, return_type;
     int strict;
     tree extra_fn_arg;
{
  int i, dummy = 0;
  tree fn_arg_types = TYPE_ARG_TYPES (TREE_TYPE (fn));
  tree decl_arg_types = args;

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

  if (IDENTIFIER_TYPENAME_P (DECL_NAME (fn))) 
    {
      /* This is a template conversion operator.  Use the return types
         as well as the argument types.  */
      fn_arg_types = scratch_tree_cons (NULL_TREE, 
                                        TREE_TYPE (TREE_TYPE (fn)),
                                        fn_arg_types);
      decl_arg_types = scratch_tree_cons (NULL_TREE,
                                          return_type,
                                          decl_arg_types);
    }

  if (extra_fn_arg != NULL_TREE)
    fn_arg_types = scratch_tree_cons (NULL_TREE, extra_fn_arg,
                                      fn_arg_types); 

  i = type_unification (DECL_INNERMOST_TEMPLATE_PARMS (fn), 
                        &TREE_VEC_ELT (targs, 0), 
                        fn_arg_types,
                        decl_arg_types,
                        explicit_targs,
                        &dummy, strict, 0);

  return i;
}


/* Type unification.

   We have a function template signature with one or more references to
   template parameters, and a parameter list we wish to fit to this
   template.  If possible, produce a list of parameters for the template
   which will cause it to fit the supplied parameter list.

   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.

   TPARMS[NTPARMS] is an array of template parameter types;
   TARGS[NTPARMS] is the array of template parameter values.  PARMS is
   the function template's signature (using TEMPLATE_PARM_IDX nodes),
   and ARGS is the argument list we're trying to match against it.

   If SUBR is 1, we're being called recursively (to unify the arguments of
   a function or method parameter of a function template), so don't zero
   out targs and don't fail on an incomplete match.

   If STRICT is 1, the match must be exact (for casts of overloaded
   addresses, explicit instantiation, and more_specialized).  */

int
type_unification (tparms, targs, parms, args, targs_in, nsubsts,
                  strict, allow_incomplete)
     tree tparms, *targs, parms, args, targs_in;
     int *nsubsts, strict, allow_incomplete;
{
  int ntparms = TREE_VEC_LENGTH (tparms);
  tree arg;
  int i;
  int r;

  bzero ((char *) targs, sizeof (tree) * ntparms);

  if (targs_in != NULL_TREE)
    {
      tree arg_vec;
      arg_vec = coerce_template_parms (tparms, targs_in, NULL_TREE, 0,
                                       0);

      if (arg_vec == error_mark_node)
        return 1;

      for (i = 0; 
           i < TREE_VEC_LENGTH (arg_vec) 
             && TREE_VEC_ELT (arg_vec, i) != NULL_TREE; 
           ++i)
        /* Insert the template argument.  It is encoded as the operands
           of NOP_EXPRs so that unify can tell that it is an explicit
           arguments.  */
        targs[i] = build1 (NOP_EXPR, NULL_TREE, TREE_VEC_ELT (arg_vec, i));
    }
  
  r = type_unification_real (tparms, targs, parms, args, nsubsts, 0,
                             strict, allow_incomplete); 

  for (i = 0, arg = targs_in; 
       arg != NULL_TREE; 
       arg = TREE_CHAIN (arg), ++i)
    if (TREE_CODE (targs[i]) == NOP_EXPR)
      targs[i] = TREE_OPERAND (targs[i], 0);

  return r;
}


static int
type_unification_real (tparms, targs, parms, args, nsubsts, subr,
                       strict, allow_incomplete)
     tree tparms, *targs, parms, args;
     int *nsubsts, subr, strict, allow_incomplete;
{
  tree parm, arg;
  int i;
  int ntparms = TREE_VEC_LENGTH (tparms);

  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);

  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)
        return 1;

      /* 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)
            {
              if (comptypes (parm, type, 1))
                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 0
      if (TREE_CODE (arg) == VAR_DECL)
        arg = TREE_TYPE (arg);
      else if (TREE_CODE_CLASS (TREE_CODE (arg)) == 'e')
        arg = TREE_TYPE (arg);
#else
      if (TREE_CODE_CLASS (TREE_CODE (arg)) != 't')
        {
          my_friendly_assert (TREE_TYPE (arg) != NULL_TREE, 293);
          if (TREE_CODE (arg) == TREE_LIST
              && TREE_TYPE (arg) == unknown_type_node
              && TREE_CODE (TREE_VALUE (arg)) == TEMPLATE_DECL)
            {
              int nsubsts, ntparms;
              tree *targs;

              /* Have to back unify here */
              arg = TREE_VALUE (arg);
              nsubsts = 0;
              ntparms = DECL_NTPARMS (arg);
              targs = (tree *) alloca (sizeof (tree) * ntparms);
              parm = expr_tree_cons (NULL_TREE, parm, NULL_TREE);
              return 
                type_unification (DECL_INNERMOST_TEMPLATE_PARMS (arg), 
                                  targs,
                                  TYPE_ARG_TYPES (TREE_TYPE (arg)),
                                  parm, NULL_TREE, &nsubsts, strict,
                                  allow_incomplete); 
            }
          arg = TREE_TYPE (arg);
        }
#endif
      if (! flag_ansi && arg == TREE_TYPE (null_node))
        {
          warning ("using type void* for NULL");
          arg = ptr_type_node;
        }

      if (! subr && TREE_CODE (arg) == REFERENCE_TYPE)
        arg = TREE_TYPE (arg);

      if (! subr && TREE_CODE (parm) != REFERENCE_TYPE)
        {
          if (TREE_CODE (arg) == FUNCTION_TYPE
              || TREE_CODE (arg) == METHOD_TYPE)
            arg = build_pointer_type (arg);
          else if (TREE_CODE (arg) == ARRAY_TYPE)
            arg = build_pointer_type (TREE_TYPE (arg));
          else
            arg = TYPE_MAIN_VARIANT (arg);
        }

      switch (unify (tparms, targs, ntparms, parm, arg, nsubsts, 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 (!targs[i])
        {
          if (!allow_incomplete)
            error ("incomplete type unification");
          return 2;
        }
  return 0;
}

/* Tail recursion is your friend.  */

static int
unify (tparms, targs, ntparms, parm, arg, nsubsts, strict)
     tree tparms, *targs, parm, arg;
     int *nsubsts, ntparms, strict;
{
  int idx;

  /* 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)
    return 1;
  if (arg == parm)
    return 0;

  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:
      (*nsubsts)++;
      idx = TEMPLATE_TYPE_IDX (parm);
      /* Check for mixed types and values.  */
      if (TREE_CODE (TREE_VALUE (TREE_VEC_ELT (tparms, idx))) != TYPE_DECL)
        return 1;

      if (!strict && targs[idx] != NULL_TREE && 
          TREE_CODE (targs[idx]) == NOP_EXPR)
        /* An explicit template argument.  Don't even try to match
           here; the overload resolution code will manage check to
           see whether the call is legal.  */ 
        return 0;

      if (strict && (TYPE_READONLY (arg) < TYPE_READONLY (parm)
                     || TYPE_VOLATILE (arg) < TYPE_VOLATILE (parm)))
        return 1;
#if 0
      /* Template type parameters cannot contain cv-quals; i.e.
         template <class T> void f (T& a, T& b) will not generate
         void f (const int& a, const int& b).  */
      if (TYPE_READONLY (arg) > TYPE_READONLY (parm)
          || TYPE_VOLATILE (arg) > TYPE_VOLATILE (parm))
        return 1;
      arg = TYPE_MAIN_VARIANT (arg);
#else
      {
        int constp = TYPE_READONLY (arg) > TYPE_READONLY (parm);
        int volatilep = TYPE_VOLATILE (arg) > TYPE_VOLATILE (parm);
        arg = cp_build_type_variant (arg, constp, volatilep);
      }
#endif
      /* Simple cases: Value already set, does match or doesn't.  */
      if (targs[idx] == arg 
          || (targs[idx] 
              && TREE_CODE (targs[idx]) == NOP_EXPR 
              && TREE_OPERAND (targs[idx], 0) == arg))
        return 0;
      else if (targs[idx])
        return 1;
      targs[idx] = arg;
      return 0;

    case TEMPLATE_TEMPLATE_PARM:
      (*nsubsts)++;
      idx = TEMPLATE_TYPE_IDX (parm);
      /* Check for mixed types and values.  */
      if (TREE_CODE (TREE_VALUE (TREE_VEC_ELT (tparms, idx))) != TEMPLATE_DECL)
        return 1;

      if (!strict && targs[idx] != NULL_TREE && 
          TREE_CODE (targs[idx]) == NOP_EXPR)
        /* An explicit template argument.  Don't even try to match
           here; the overload resolution code will manage check to
           see whether the call is legal.  */ 
        return 0;

      if (CLASSTYPE_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 = CLASSTYPE_TI_TEMPLATE (parm);
            tree parmvec = CLASSTYPE_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 Allcator = allocator> 
                   class vector.  */

            if (coerce_template_parms (argtmplvec, parmvec, parmtmpl, 1, 1)
                == error_mark_node)
              return 1;
          
            /* Deduce arguments T, i from TT<T> or TT<i>.  */
            for (i = 0; i < TREE_VEC_LENGTH (parmvec); ++i)
              {
                tree t = TREE_VEC_ELT (parmvec, i);
                if (TREE_CODE (t) != TEMPLATE_TYPE_PARM
                    && TREE_CODE (t) != TEMPLATE_TEMPLATE_PARM
                    && TREE_CODE (t) != TEMPLATE_CONST_PARM)
                  continue;

                /* This argument can be deduced.  */

                if (unify (tparms, targs, ntparms, t, 
                           TREE_VEC_ELT (argvec, i), nsubsts, strict))
                  return 1;
              }
          }
          arg = CLASSTYPE_TI_TEMPLATE (arg);
        }

      /* Simple cases: Value already set, does match or doesn't.  */
      if (targs[idx] == arg 
          || (targs[idx] 
              && TREE_CODE (targs[idx]) == NOP_EXPR 
              && TREE_OPERAND (targs[idx], 0) == arg))
        return 0;
      else if (targs[idx])
        return 1;
      targs[idx] = arg;
      return 0;

    case TEMPLATE_CONST_PARM:
      (*nsubsts)++;
      idx = TEMPLATE_CONST_IDX (parm);
      if (targs[idx])
        {
          int i = cp_tree_equal (targs[idx], arg);
          if (i == 1)
            return 0;
          else if (i == 0)
            return 1;
          else
            my_friendly_abort (42);
        }

      targs[idx] = copy_to_permanent (arg);
      return 0;

    case POINTER_TYPE:
      if (TREE_CODE (arg) == RECORD_TYPE && TYPE_PTRMEMFUNC_FLAG (arg))
        return unify (tparms, targs, ntparms, parm,
                      TYPE_PTRMEMFUNC_FN_TYPE (arg), nsubsts, strict);

      if (TREE_CODE (arg) != POINTER_TYPE)
        return 1;
      return unify (tparms, targs, ntparms, TREE_TYPE (parm), TREE_TYPE (arg),
                    nsubsts, strict);

    case REFERENCE_TYPE:
      if (TREE_CODE (arg) == REFERENCE_TYPE)
        arg = TREE_TYPE (arg);
      return unify (tparms, targs, ntparms, TREE_TYPE (parm), arg,
                    nsubsts, strict);

    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, ntparms, TYPE_DOMAIN (parm),
                    TYPE_DOMAIN (arg), nsubsts, strict) != 0)
        return 1;
      return unify (tparms, targs, ntparms, TREE_TYPE (parm), TREE_TYPE (arg),
                    nsubsts, strict);

    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)
        {
          if (TYPE_MIN_VALUE (parm) && TYPE_MIN_VALUE (arg)
              && unify (tparms, targs, ntparms, TYPE_MIN_VALUE (parm),
                        TYPE_MIN_VALUE (arg), nsubsts, strict))
            return 1;
          if (TYPE_MAX_VALUE (parm) && TYPE_MAX_VALUE (arg)
              && unify (tparms, targs, ntparms, TYPE_MAX_VALUE (parm),
                        TYPE_MAX_VALUE (arg), nsubsts, strict))
            return 1;
        }
      else if (TREE_CODE (parm) == REAL_TYPE
               && 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 MINUS_EXPR:
      {
        tree t1, t2;
        t1 = TREE_OPERAND (parm, 0);
        t2 = TREE_OPERAND (parm, 1);
        return unify (tparms, targs, ntparms, t1,
                      fold (build (PLUS_EXPR, integer_type_node, arg, t2)),
                      nsubsts, strict);
      }

    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, ntparms,
                     TREE_VEC_ELT (parm, i), TREE_VEC_ELT (arg, i),
                     nsubsts, strict))
            return 1;
        return 0;
      }

    case RECORD_TYPE:
      if (TYPE_PTRMEMFUNC_FLAG (parm))
        return unify (tparms, targs, ntparms, TYPE_PTRMEMFUNC_FN_TYPE (parm),
                      arg, nsubsts, strict);

      /* Allow trivial conversions.  */
      if (TREE_CODE (arg) != RECORD_TYPE
          || TYPE_READONLY (parm) < TYPE_READONLY (arg)
          || TYPE_VOLATILE (parm) < TYPE_VOLATILE (arg))
        return 1;

      if (CLASSTYPE_TEMPLATE_INFO (parm) && uses_template_parms (parm))
        {
          tree t = NULL_TREE;
          if (flag_ansi_overloading && ! strict)
            t = get_template_base (CLASSTYPE_TI_TEMPLATE (parm), arg);
          else if
            (CLASSTYPE_TEMPLATE_INFO (arg)
             && CLASSTYPE_TI_TEMPLATE (parm) == CLASSTYPE_TI_TEMPLATE (arg))
            t = arg;
          if (! t || t == error_mark_node)
            return 1;

          return unify (tparms, targs, ntparms, CLASSTYPE_TI_ARGS (parm),
                        CLASSTYPE_TI_ARGS (t), nsubsts, strict);
        }
      else if (TYPE_MAIN_VARIANT (parm) != TYPE_MAIN_VARIANT (arg))
        return 1;
      return 0;

    case METHOD_TYPE:
      if (TREE_CODE (arg) != METHOD_TYPE)
        return 1;
      goto check_args;

    case FUNCTION_TYPE:
      if (TREE_CODE (arg) != FUNCTION_TYPE)
        return 1;
     check_args:
      if (unify (tparms, targs, ntparms, TREE_TYPE (parm),
                 TREE_TYPE (arg), nsubsts, strict))
        return 1;
      return type_unification_real (tparms, targs, TYPE_ARG_TYPES (parm),
                                    TYPE_ARG_TYPES (arg), nsubsts, 1, 
                                    strict, 0);

    case OFFSET_TYPE:
      if (TREE_CODE (arg) != OFFSET_TYPE)
        return 1;
      if (unify (tparms, targs, ntparms, TYPE_OFFSET_BASETYPE (parm),
                 TYPE_OFFSET_BASETYPE (arg), nsubsts, strict))
        return 1;
      return unify (tparms, targs, ntparms, TREE_TYPE (parm),
                    TREE_TYPE (arg), nsubsts, strict);

    case CONST_DECL:
      if (arg != decl_constant_value (parm))
        return 1;
      return 0;

    default:
      sorry ("use of `%s' in template type unification",
             tree_code_name [(int) TREE_CODE (parm)]);
      return 1;
    }
}
\f
void
mark_decl_instantiated (result, extern_p)
     tree result;
     int extern_p;
{
  if (DECL_TEMPLATE_INSTANTIATION (result))
    SET_DECL_EXPLICIT_INSTANTIATION (result);

  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;

      /* For WIN32 we also want to put explicit instantiations in
         linkonce sections.  */
      if (supports_one_only () && ! SUPPORTS_WEAK && TREE_PUBLIC (result))
        make_decl_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 (pat1, pat2, explicit_args);
  if (targs)
    {
      --winner;
    }

  targs = get_bindings (pat2, 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.  */

tree 
get_bindings (fn, decl, explicit_args)
     tree fn, decl, explicit_args;
{
  int ntparms = DECL_NTPARMS (fn);
  tree targs = make_scratch_vec (ntparms);
  tree decl_arg_types = TYPE_ARG_TYPES (TREE_TYPE (decl));
  tree extra_fn_arg = NULL_TREE;
  int i;

  if (DECL_STATIC_FUNCTION_P (fn) 
      && DECL_NONSTATIC_MEMBER_FUNCTION_P (decl))
    {
      /* Sometimes we are trying to figure out what's being
         specialized by a declaration that looks like a method, and it
         turns out to be a static member function.  */
      if (CLASSTYPE_TEMPLATE_INFO (DECL_REAL_CONTEXT (fn))
          && !is_member_template (fn))
        /* The natural thing to do here seems to be to remove the
           spurious `this' parameter from the DECL, but that prevents
           unification from making use of the class type.  So,
           instead, we have fn_type_unification add to the parameters
           for FN.  */
        extra_fn_arg = build_pointer_type (DECL_REAL_CONTEXT (fn));
      else
        /* In this case, though, adding the extra_fn_arg can confuse
           things, so we remove from decl_arg_types instead.  */
        decl_arg_types = TREE_CHAIN (decl_arg_types);
    }

  i = fn_type_unification (fn, explicit_args, targs, 
                           decl_arg_types,
                           TREE_TYPE (TREE_TYPE (decl)),
                           1,
                           extra_fn_arg);

  if (i == 0)
    {
      /* Check to see that the resulting return type is also OK.  */
      tree t = tsubst (TREE_TYPE (TREE_TYPE (fn)),
                       targs,
                       DECL_NTPARMS (fn),
                       NULL_TREE);

      if (!comptypes(t, TREE_TYPE (TREE_TYPE (decl)), 1))
        return NULL_TREE;

      return targs;
    }

  return NULL_TREE;
}

static tree
get_class_bindings (tparms, parms, args)
     tree tparms, parms, args;
{
  int i, dummy, ntparms = TREE_VEC_LENGTH (tparms);
  tree vec = make_temp_vec (ntparms);

  for (i = 0; i < TREE_VEC_LENGTH (parms); ++i)
    {
      switch (unify (tparms, &TREE_VEC_ELT (vec, 0), ntparms,
                     TREE_VEC_ELT (parms, i), TREE_VEC_ELT (args, i),
                     &dummy, 1))
        {
        case 0:
          break;
        case 1:
          return NULL_TREE;
        }
    }

  for (i =  0; i < ntparms; ++i)
    if (! TREE_VEC_ELT (vec, i))
      return NULL_TREE;

  return vec;
}

/* 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.  */

tree
most_specialized (fns, decl, explicit_args)
     tree fns, decl, explicit_args;
{
  tree fn, champ, args, *p;
  int fate;

  for (p = &fns; *p; )
    {
      args = get_bindings (TREE_VALUE (*p), decl, explicit_args);
      if (args)
        {
          p = &TREE_CHAIN (*p);
        }
      else
        *p = TREE_CHAIN (*p);
    }

  if (! fns)
    return NULL_TREE;

  fn = fns;
  champ = TREE_VALUE (fn);
  fn = TREE_CHAIN (fn);
  for (; fn; fn = TREE_CHAIN (fn))
    {
      fate = more_specialized (champ, TREE_VALUE (fn), explicit_args);
      if (fate == 1)
        ;
      else
        {
          if (fate == 0)
            {
              fn = TREE_CHAIN (fn);
              if (! fn)
                return error_mark_node;
            }
          champ = TREE_VALUE (fn);
        }
    }

  for (fn = fns; fn && TREE_VALUE (fn) != champ; fn = TREE_CHAIN (fn))
    {
      fate = more_specialized (champ, TREE_VALUE (fn), explicit_args);
      if (fate != 1)
        return error_mark_node;
    }

  return champ;
}

/* Return the most specialized of the class template specializations in
   SPECS that can produce an instantiation matching ARGS.  */

tree
most_specialized_class (specs, mainargs)
     tree specs, mainargs;
{
  tree list = NULL_TREE, t, args, champ;
  int fate;

  for (t = specs; t; t = TREE_CHAIN (t))
    {
      args = get_class_bindings (TREE_VALUE (t), TREE_PURPOSE (t), mainargs);
      if (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 name;
  tree fn;
  tree result = NULL_TREE;
  int extern_p = 0;

  if (! DECL_LANG_SPECIFIC (decl))
    {
      cp_error ("explicit instantiation of non-template `%#D'", decl);
      return;
    }

  /* If we've already seen this template instance, use it.  */
  if (TREE_CODE (decl) == VAR_DECL)
    {
      result = lookup_field (DECL_CONTEXT (decl), DECL_NAME (decl), 0, 0);
      if (result && TREE_CODE (result) != VAR_DECL)
        result = NULL_TREE;
    }
  else if (TREE_CODE (decl) != FUNCTION_DECL)
    {
      cp_error ("explicit instantiation of `%#D'", decl);
      return;
    }
  else if (DECL_TEMPLATE_INSTANTIATION (decl))
    result = decl;

  if (! result)
    {
      cp_error ("no matching template for `%D' found", decl);
      return;
    }

  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])
    extern_p = 1;
  else
    cp_error ("storage class `%D' applied to template instantiation",
              storage);

  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 (! IS_AGGR_TYPE (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)
    /* OK */;
  else 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;
    }

  /* We've already instantiated this.  */
  if (CLASSTYPE_EXPLICIT_INSTANTIATION (t) && ! CLASSTYPE_INTERFACE_ONLY (t)
      && extern_p)
    return;

  if (! CLASSTYPE_TEMPLATE_SPECIALIZATION (t))
    {
      mark_class_instantiated (t, extern_p);
      repo_template_instantiated (t, extern_p);
    }

  if (nomem_p)
    return;

  {
    tree tmp;

    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)))
        do_type_instantiation (TYPE_MAIN_DECL (TREE_VALUE (tmp)), storage);
  }
}

tree
instantiate_decl (d)
     tree d;
{
  tree ti = DECL_TEMPLATE_INFO (d);
  tree tmpl = TI_TEMPLATE (ti);
  tree args = TI_ARGS (ti);
  tree td;
  tree decl_pattern, code_pattern;
  tree save_ti;
  int nested = in_function_p ();
  int d_defined;
  int pattern_defined;
  int line = lineno;
  char *file = input_filename;

  for (td = tmpl; DECL_TEMPLATE_INSTANTIATION (td); )
    td = DECL_TI_TEMPLATE (td);

  /* In the case of a member template, decl_pattern is the partially
     instantiated declaration (in the instantiated class), and code_pattern
     is the original template definition.  */
  decl_pattern = DECL_TEMPLATE_RESULT (tmpl);
  code_pattern = DECL_TEMPLATE_RESULT (td);

  if (TREE_CODE (d) == FUNCTION_DECL)
    {
      d_defined = (DECL_INITIAL (d) != NULL_TREE);
      pattern_defined = (DECL_INITIAL (code_pattern) != NULL_TREE);
    }
  else
    {
      d_defined = ! DECL_IN_AGGR_P (d);
      pattern_defined = ! DECL_IN_AGGR_P (code_pattern);
    }

  if (d_defined)
    return d;

  if (TREE_CODE (d) == FUNCTION_DECL) 
    {
      tree spec = retrieve_specialization (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;

  push_to_top_level ();
  lineno = DECL_SOURCE_LINE (d);
  input_filename = DECL_SOURCE_FILE (d);

  /* We need to set up DECL_INITIAL regardless of pattern_defined if the
     variable is a static const initialized in the class body.  */
  if (TREE_CODE (d) == VAR_DECL
      && ! DECL_INITIAL (d) && DECL_INITIAL (code_pattern))
    {
      pushclass (DECL_CONTEXT (d), 2);
      DECL_INITIAL (d) = tsubst_expr (DECL_INITIAL (code_pattern), args,
                                      TREE_VEC_LENGTH (args), tmpl);
      cp_finish_decl (d, DECL_INITIAL (d), NULL_TREE, 0, LOOKUP_NORMAL);
    }

  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;

  /* Defer all templates except inline functions used in another function.  */
  if (! pattern_defined
      || (! (TREE_CODE (d) == FUNCTION_DECL && DECL_INLINE (d) && nested)
          && ! at_eof))
    {
      add_pending_template (d);
      goto out;
    }

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

  /* Trick tsubst into giving us a new decl in case the template changed.  */
  save_ti = DECL_TEMPLATE_INFO (decl_pattern);
  DECL_TEMPLATE_INFO (decl_pattern) = NULL_TREE;
  td = tsubst (decl_pattern, args, TREE_VEC_LENGTH (args), tmpl);
  SET_DECL_IMPLICIT_INSTANTIATION (td);
  DECL_TEMPLATE_INFO (decl_pattern) = save_ti;

  /* And set up DECL_INITIAL, since tsubst doesn't.  */
  if (TREE_CODE (td) == VAR_DECL)
    {
      pushclass (DECL_CONTEXT (d), 2);
      DECL_INITIAL (td) = tsubst_expr (DECL_INITIAL (code_pattern), args,
                                       TREE_VEC_LENGTH (args), tmpl);
      popclass (1);
    }

  if (TREE_CODE (d) == FUNCTION_DECL)
    {
      /* Convince duplicate_decls to use the DECL_ARGUMENTS from the
         new decl.  */ 
      DECL_INITIAL (td) = error_mark_node;

      if (DECL_TEMPLATE_SPECIALIZATION (td) && !DECL_TEMPLATE_INFO (td))
        /* Set up the information about what is being specialized. */
        DECL_TEMPLATE_INFO (td) = DECL_TEMPLATE_INFO (d);
    }
  duplicate_decls (td, d);
  if (TREE_CODE (d) == FUNCTION_DECL)
    DECL_INITIAL (td) = 0;

  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,
                          TREE_VEC_LENGTH (args), 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, TREE_VEC_LENGTH (args), tmpl);

      finish_function (lineno, 0, nested);
    }

out:
  lineno = line;
  input_filename = file;

  pop_from_top_level ();
  pop_tinst_level ();

  return d;
}

tree
tsubst_chain (t, argvec)
     tree t, argvec;
{
  if (t)
    {
      tree first = tsubst (t, argvec,
                           TREE_VEC_LENGTH (argvec), NULL_TREE);
      tree last = first;

      for (t = TREE_CHAIN (t); t; t = TREE_CHAIN (t))
        {
          tree x = tsubst (t, argvec, TREE_VEC_LENGTH (argvec), NULL_TREE);
          TREE_CHAIN (last) = x;
          last = x;
        }

      return first;
    }
  return NULL_TREE;
}

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,
                              TREE_VEC_LENGTH (argvec), NULL_TREE);
      tree val = tsubst_expr (TREE_VALUE (t), argvec,
                              TREE_VEC_LENGTH (argvec), 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;
}

/* Instantiate an enumerated type.  Used by instantiate_class_template and
   tsubst_expr.  */

static tree
tsubst_enum (tag, args, nargs, field_chain)
     tree tag, args;
     int nargs;
     tree * field_chain;
{
  extern tree current_local_enum;
  tree prev_local_enum = current_local_enum;

  tree newtag = start_enum (TYPE_IDENTIFIER (tag));
  tree e, values = NULL_TREE;

  for (e = TYPE_VALUES (tag); e; e = TREE_CHAIN (e))
    {
      tree elt = build_enumerator (TREE_PURPOSE (e),
                                   tsubst_expr (TREE_VALUE (e), args,
                                                nargs, NULL_TREE));
      TREE_CHAIN (elt) = values;
      values = elt;
    }

  finish_enum (newtag, values);

  if (NULL != field_chain)
    *field_chain = grok_enum_decls (NULL_TREE);

  current_local_enum = prev_local_enum;

  return newtag;
}