[C++ PATCH] Fix default arg processing of template template parm

[Kriang Lerdsuwanakij]

Hi

The current GCC doesn't support the default argument processing behavior
of template template parameters.  This is important when the template
template parameter is intended for standard containers such as 
std::vector.  To declare a class template taking std::vector as its 
argument, we have to use the syntax

        template<template<class T, class U = std::allocator<T> > class TT>
        struct C {
                TT<int> t;      // Require default argument of U
        };
        C<std::vector> c;

The default argument of U that depends on other parameters (T in this case)
is not correctly expanded.  The appended patch fixes this problem.

Bootstrapped and tested on i686-linux-gnu with no regressions.
Ok to install in the main trunk?

--Kriang


2001-10-12  Kriang Lerdsuwanakij  <lerdsuwa@users.sourceforge.net>

        * pt.c (lookup_template_class): Build complete template arguments
        for BOUND_TEMPLATE_TEMPLATE_PARM.

diff -cprN gcc-main-save3/gcc/cp/pt.c gcc-main-new/gcc/cp/pt.c
*** gcc-main-save3/gcc/cp/pt.c  Sat Sep 22 22:46:23 2001
--- gcc-main-new/gcc/cp/pt.c    Fri Oct 12 20:28:42 2001
*************** lookup_template_class (d1, arglist, in_d
*** 3918,3923 ****
--- 3918,3936 ----
  
        parmlist = DECL_INNERMOST_TEMPLATE_PARMS (template);
  
+       /* Consider an example where a template template parameter declared as
+ 
+          template <class T, class U = std::allocator<T> > class TT
+ 
+        The template parameter level of T and U are one level larger than 
+        of TT.  To proper process the default argument of U, say when an 
+        instantiation `TT<int>' is seen, we need to build the full
+        arguments containing {int} as the innermost level.  Outer levels
+        can be obtained from `current_template_args ()'.  */
+ 
+       if (processing_template_decl)
+       arglist = add_to_template_args (current_template_args (), arglist);
+ 
        arglist2 = coerce_template_parms (parmlist, arglist, template,
                                          complain, /*require_all_args=*/1);
        if (arglist2 == error_mark_node)
diff -cprN gcc-main-save3/gcc/testsuite/g++.dg/template/ttp2.C gcc-main-new/gcc/testsuite/g++.dg/template/ttp2.C
*** gcc-main-save3/gcc/testsuite/g++.dg/template/ttp2.C Thu Jan  1 07:00:00 1970
--- gcc-main-new/gcc/testsuite/g++.dg/template/ttp2.C   Thu Oct 11 22:26:42 2001
***************
*** 0 ****
--- 1,17 ----
+ // Copyright (C) 2001 Free Software Foundation
+ // Contributed by Kriang Lerdsuwanakij <lerdsuwa@users.sourceforge.net>
+ // { dg-do compile }
+ 
+ template <class U> struct Alloc {};
+ 
+ template <class T, class U = Alloc<T> > struct Vector {};
+ 
+ template <template <class T, class U = Alloc<T> > class TT>
+ struct C {
+       TT<int> tt;
+ };
+ 
+ int main()
+ {
+       C<Vector> c;
+ }