pt.c (mabybe_get_template_decl_from_type_decl): New function.

[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 "system.h"
#include "obstack.h"

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

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

extern struct obstack permanent_obstack;

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

tree current_template_parms;
HOST_WIDE_INT processing_template_decl;

tree pending_templates;
static tree *template_tail = &pending_templates;

tree maybe_templates;
static tree *maybe_template_tail = &maybe_templates;

int minimal_parse_mode;

int processing_specialization;
int processing_explicit_instantiation;
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, tree));
static tree coerce_template_parms PROTO((tree, tree, tree, int, int, int));
static tree tsubst_enum PROTO((tree, tree, 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 tree complete_template_args PROTO((tree, tree, int));
static void note_template_header PROTO((int));
static tree maybe_fold_nontype_arg PROTO((tree));
static tree convert_nontype_argument PROTO((tree, tree));
static tree get_bindings_overload PROTO((tree, tree, tree));
static int for_each_template_parm PROTO((tree, tree_fn_t, void*));
static tree build_template_parm_index PROTO((int, int, int, tree, tree));
static tree original_template PROTO((tree));
static int inline_needs_template_parms PROTO((tree));
static void push_inline_template_parms_recursive PROTO((tree, int));
static tree retrieve_specialization PROTO((tree, tree));
static void register_specialization PROTO((tree, tree, tree));
static void print_candidates PROTO((tree));
static tree reduce_template_parm_level PROTO((tree, tree, int));
static tree build_template_decl PROTO((tree, tree));
static int mark_template_parm PROTO((tree, void *));
static tree tsubst_friend_function PROTO((tree, tree));
static tree get_bindings_real PROTO((tree, tree, tree, int));
static int template_decl_level PROTO((tree));
static tree maybe_get_template_decl_from_type_decl PROTO((tree));

/* 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 == NULL_TREE || decl == void_type_node)
    return NULL_TREE;
  else if (TREE_CODE (decl) == TREE_LIST)
    {
      /* Assume that the class is the only declspec.  */
      decl = TREE_VALUE (decl);
      if (IS_AGGR_TYPE (decl) && CLASSTYPE_TEMPLATE_INFO (decl)
          && ! CLASSTYPE_TEMPLATE_SPECIALIZATION (decl))
        {
          tree tmpl = CLASSTYPE_TI_TEMPLATE (decl);
          check_member_template (tmpl);
          return tmpl;
        }
      return NULL_TREE;
    }
  else if (DECL_TEMPLATE_INFO (decl))
    {
      if (!DECL_TEMPLATE_SPECIALIZATION (decl))
        {
          check_member_template (DECL_TI_TEMPLATE (decl));
          return DECL_TI_TEMPLATE (decl);
        }
      else
        return decl;
    } 
  else
    cp_error ("invalid member template declaration `%D'", decl);
        

  return error_mark_node;
}

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

   A<T>::B<U> has depth two, while A<T> has depth one.  Also,
   both A<T>::B<int> and A<int>::B<U> have depth one.  */

int 
template_class_depth (type)
     tree type;
{
  int depth;

  for (depth = 0; type && TREE_CODE (type) != FUNCTION_DECL;
       type = TYPE_CONTEXT (type))
    if (CLASSTYPE_TEMPLATE_INFO (type)
        && PRIMARY_TEMPLATE_P (CLASSTYPE_TI_TEMPLATE (type))
        && uses_template_parms (CLASSTYPE_TI_ARGS (type)))
      ++depth;

  return depth;
}

/* Return the original template for this decl, disregarding any
   specializations.  */

static tree
original_template (decl)
     tree decl;
{
  while (DECL_TEMPLATE_INFO (decl))
    decl = DECL_TI_TEMPLATE (decl);
  return decl;
}

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

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

  return (list_length (DECL_TEMPLATE_PARMS (original_template (decl)))
          > (processing_template_decl + DECL_TEMPLATE_SPECIALIZATION (decl)));
}

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

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

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

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

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

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

        case PARM_DECL:
          {
            /* Make a CONST_DECL as is done in process_template_parm. */
            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);
        }
    }
}

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

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

  if (! inline_needs_template_parms (decl))
    return;

  parms = DECL_TEMPLATE_PARMS (original_template (decl));

  levels = list_length (parms) - processing_template_decl;

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

  push_inline_template_parms_recursive (parms, levels);
}

/* Undo the effects of begin_member_template_processing. */

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

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

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

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

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

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

   then neither C<int>::f<char> nor C<T>::f<double> is considered
   to be a member template.  */

int
is_member_template (t)
     tree t;
{
  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;

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

      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);
      else
        tmpl = NULL_TREE;

      if (tmpl
          /* If there are more levels of template parameters than
             there are template classes surrounding the declaration,
             then we have a member template.  */
          && (list_length (DECL_TEMPLATE_PARMS (tmpl)) > 
              template_class_depth (DECL_CLASS_CONTEXT (t))))
        return 1;
    }

  return 0;
}

/* Return a new template argument vector which contains all of ARGS
   for all outer templates TYPE is contained in, but has as its 
   innermost set of arguments the EXTRA_ARGS.  If UNBOUND_ONLY, we
   are only interested in unbound template arguments, not arguments from
   enclosing templates that have been instantiated already.  */

static tree
complete_template_args (tmpl, extra_args, unbound_only)
     tree tmpl, extra_args;
     int unbound_only;
{
  /* depth is the number of levels of enclosing args we're adding.  */
  int depth, i;
  tree args, new_args, spec_args = NULL_TREE;
  
  my_friendly_assert (TREE_CODE (tmpl) == TEMPLATE_DECL, 0);
  my_friendly_assert (TREE_CODE (extra_args) == TREE_VEC, 0);

  if (DECL_TEMPLATE_INFO (tmpl) && !unbound_only)
    {
      /* A specialization of a member template of a template class shows up
         as a TEMPLATE_DECL with DECL_TEMPLATE_SPECIALIZATION set.
         DECL_TI_ARGS is the specialization args, and DECL_TI_TEMPLATE
         is the template being specialized.  */
      if (DECL_TEMPLATE_SPECIALIZATION (tmpl))
        {
          spec_args = DECL_TI_ARGS (tmpl);
          tmpl = DECL_TI_TEMPLATE (tmpl);
        }

      if (DECL_TEMPLATE_INFO (tmpl))
        {
          /* A partial instantiation of a member template shows up as a
             TEMPLATE_DECL with DECL_TEMPLATE_INFO.  DECL_TI_ARGS is
             all the bound template arguments.  */
          args = DECL_TI_ARGS (tmpl);
          if (TREE_CODE (TREE_VEC_ELT (args, 0)) != TREE_VEC)
            depth = 1;
          else
            depth = TREE_VEC_LENGTH (args);
        }
      else
        /* If we are a specialization, we might have no previously bound
           template args.  */
        depth = 0;

      new_args = make_tree_vec (depth + 1 + (!!spec_args));

      if (depth == 1)
        TREE_VEC_ELT (new_args, 0) = args;
      else
        for (i = 0; i < depth; ++i)
          TREE_VEC_ELT (new_args, i) = TREE_VEC_ELT (args, i);
    }
  else
    {
      tree type;
      int skip;

      /* For unbound args, we have to do more work.  We are getting bindings
         for the innermost args from extra_args, so we start from our
         context and work out until we've seen all the args.  We need to
         do it this way to handle partial specialization.  */

      depth = list_length (DECL_TEMPLATE_PARMS (tmpl)) - 1;
      if (depth == 0)
        return extra_args;

      new_args = make_tree_vec (depth + 1);

      /* If this isn't a member template, extra_args is for the innermost
         template class, so skip over it.  */
      skip = (! is_member_template (tmpl));

      type = DECL_REAL_CONTEXT (tmpl);
      for (i = depth; i; type = TYPE_CONTEXT (type))
        if (PRIMARY_TEMPLATE_P (CLASSTYPE_TI_TEMPLATE (type)))
          {
            if (skip)
              skip = 0;
            else
              {
                --i;
                TREE_VEC_ELT (new_args, i) = CLASSTYPE_TI_ARGS (type);
              }
          }
    }

  TREE_VEC_ELT (new_args, depth) = extra_args;

  if (spec_args)
    TREE_VEC_ELT (new_args, depth + 1) = spec_args;

  return new_args;
}

/* 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)
    {
      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)))
        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),
                                targs,
                                NULL_TREE,
                                NULL_TREE,  
                                targs_in,
                                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",
                  template_id);
      
      return NULL_TREE;
    }
  else if (TREE_CHAIN (templates) != NULL_TREE) 
    {
    ambiguous:
      if (complain)
        {
          cp_error ("ambiguous template specialization `%D'",
                    template_id);
          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. 
   
   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)
    {
      tree t = TYPE_ARG_TYPES (TREE_TYPE (decl));
      for (; t; t = TREE_CHAIN (t))
        if (TREE_PURPOSE (t))
          {
            cp_pedwarn
              ("default argument specified in explicit specialization");
            break;
          }
    }

  if (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_NAMESPACE_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;
                }

              name = is_constructor ? ctor_identifier : dtor_identifier;
            }

          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);
              last_function_parms = TREE_CHAIN (last_function_parms);
            }

          /* 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;
}


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

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

  return t;
}


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

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

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

  return TEMPLATE_PARM_DESCENDANTS (index);
}

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

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

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

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

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

  if (!is_type)
    {
      my_friendly_assert (TREE_CODE (TREE_PURPOSE (parm)) == TREE_LIST, 260);
      /* is a const-param */
      parm = grokdeclarator (TREE_VALUE (parm), TREE_PURPOSE (parm),
                             PARM, 0, NULL_TREE);
      /* 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));
      if (TREE_PERMANENT (parm) == 0)
        {
          parm = copy_node (parm);
          TREE_PERMANENT (parm) = 1;
        }
      decl = build_decl (CONST_DECL, DECL_NAME (parm), TREE_TYPE (parm));
      DECL_INITIAL (parm) = DECL_INITIAL (decl) 
        = build_template_parm_index (idx, processing_template_decl,
                                     processing_template_decl,
                                     decl, TREE_TYPE (parm));
    }
  else
    {
      tree t;
      parm = TREE_VALUE (parm);
      
      if (parm && TREE_CODE (parm) == TEMPLATE_DECL)
        {
          t = make_lang_type (TEMPLATE_TEMPLATE_PARM);
          /* This is for distinguishing between real templates and template 
             template parameters */
          TREE_TYPE (parm) = t;
          TREE_TYPE (DECL_TEMPLATE_RESULT (parm)) = t;
          decl = parm;
        }
      else
        {
          t = make_lang_type (TEMPLATE_TYPE_PARM);
          /* parm is either IDENTIFIER_NODE or NULL_TREE */
          decl = build_decl (TYPE_DECL, parm, t);
        }
        
      CLASSTYPE_GOT_SEMICOLON (t) = 1;
      TYPE_NAME (t) = decl;
      TYPE_STUB_DECL (t) = decl;
      parm = decl;
      TEMPLATE_TYPE_PARM_INDEX (t)
        = build_template_parm_index (idx, processing_template_decl, 
                                     processing_template_decl,
                                     decl, TREE_TYPE (parm));
    }
  SET_DECL_ARTIFICIAL (decl);
  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;
}

struct template_parm_data
{
  int level;
  int* parms;
};

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

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

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

  if (level == tpd->level)
    tpd->parms[idx] = 1;

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

/* 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;
  tree info;
  tree ctx;
  int primary;
  int is_friend = (TREE_CODE (decl) == FUNCTION_DECL
                   && DECL_FRIEND_P (decl));

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

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

  if (info && TREE_CODE (info) == FUNCTION_DECL)
    primary = 0;
  else if (! info
           || (TYPE_BEING_DEFINED (info) && template_header_count
               && ! processing_specialization)
           || (template_header_count > template_class_depth (info)))
    primary = 1;
  else
    primary = 0;

  if (primary)
    {
      if (current_lang_name == lang_name_c)
        cp_error ("template with C linkage");
      if (TREE_CODE (decl) == TYPE_DECL && ANON_AGGRNAME_P (DECL_NAME (decl)))
        cp_error ("template class without a name");
    }

  /* 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);

      /* We check that each of the template parameters given in the
         partial specialization is used in the argument list to the
         specialization.  For example:
         
           template <class T> struct S;
           template <class T> struct S<T*>;

         The second declaration is OK because `T*' uses the template
         parameter T, whereas
       
           template <class T> struct S<int>;

         is no good.  Even trickier is:

           template <class T>
           struct S1
           {
              template <class U>
              struct S2;
              template <class U>
              struct S2<T>;
           };
           
         The S2<T> declaration is actually illegal; it is a
         full-specialization.  Of course, 

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

         or some such would have been OK.  */
      int  i;
      struct template_parm_data tpd;
      int ntparms = TREE_VEC_LENGTH (TREE_VALUE (current_template_parms));
      int did_error_intro = 0;

      tpd.level = TREE_INT_CST_HIGH (TREE_PURPOSE (current_template_parms));
      tpd.parms = alloca (sizeof (int) * ntparms);
      for (i = 0; i < ntparms; ++i)
        tpd.parms[i] = 0;
      for (i = 0; i < TREE_VEC_LENGTH (mainargs); ++i)
        for_each_template_parm (TREE_VEC_ELT (mainargs, i),
                                &mark_template_parm,
                                &tpd);
      for (i = 0; i < ntparms; ++i)
        if (tpd.parms[i] == 0)
          {
            /* One of the template parms was not used in the
               specialization.  */
            if (!did_error_intro)
              {
                cp_error ("template parameters not used in partial specialization:");
                did_error_intro = 1;
              }

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

      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)
      || (is_friend && !DECL_TEMPLATE_INFO (decl)))
    {
      if (DECL_LANG_SPECIFIC (decl)
          && DECL_TEMPLATE_INFO (decl)
          && DECL_TI_TEMPLATE (decl))
        tmpl = DECL_TI_TEMPLATE (decl);
      else
        {
          tmpl = build_template_decl (decl, current_template_parms);
          
          if (DECL_LANG_SPECIFIC (decl)
              && DECL_TEMPLATE_SPECIALIZATION (decl))
            {
              /* A specialization of a member template of a template
                 class. */
              SET_DECL_TEMPLATE_SPECIALIZATION (tmpl);
              DECL_TEMPLATE_INFO (tmpl) = DECL_TEMPLATE_INFO (decl);
              DECL_TEMPLATE_INFO (decl) = NULL_TREE;
            }
        }
    }
  else
    {
      tree 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 = innermost_args (args, 0);

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

  if (! ctx && primary)
    /* The check of PRIMARY ensures that we do not try to push a
       global template friend declared in a template class; such a
       thing may well depend on the template parameters of the class.  */
    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);
}

/* Called when a class template TYPE is redeclared, e.g.:

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

void 
redeclare_class_template (type)
     tree type;
{
  tree tmpl = CLASSTYPE_TI_TEMPLATE (type);
  tree tmpl_parms = DECL_INNERMOST_TEMPLATE_PARMS (tmpl);
  tree parms = INNERMOST_TEMPLATE_PARMS (current_template_parms);
  int i;

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

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

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

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

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

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

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

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

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

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

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

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

  if (is_overloaded_fn (expr))
    /* OK for now.  We'll check that it has external linkage later.
       Check this first since if expr_type is the unknown_type_node
       we would otherwise complain below.  */
    ;
  else if (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;
      tree e = expr;
      STRIP_NOPS (e);

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

      referent = TREE_OPERAND (e, 0);
      STRIP_NOPS (referent);
      
      if (TREE_CODE (referent) == STRING_CST)
        {
          cp_error ("string literal %E is not a valid template argument", 
                    referent);
          error ("because it is the address of an object with static linkage");
          return NULL_TREE;
        }

      if (is_overloaded_fn (referent))
        /* We'll check that it has external linkage later.  */
        ;
      else if (TREE_CODE (referent) != VAR_DECL)
        goto bad_argument;
      else if (!TREE_PUBLIC (referent))
        {
          cp_error ("address of non-extern `%E' cannot be used as template argument", referent); 
          return error_mark_node;
        }
    }
  else if (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.
   
   If IS_TMPL_PARM is non-zero,  we will coercing parameters of template 
   template arguments.  In this case, ARGLIST is a chain of TREE_LIST
   nodes containing TYPE_DECL, TEMPLATE_DECL or PARM_DECL.  */

static tree
coerce_template_parms (parms, arglist, in_decl,
                       complain,
                       require_all_arguments,
                       is_tmpl_parm)
     tree parms, arglist;
     tree in_decl;
     int complain;
     int require_all_arguments;
     int is_tmpl_parm;
{
  int nparms, nargs, i, lost = 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
    {
      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, in_decl);
          else
            arg = tsubst_expr (TREE_PURPOSE (parm), vec, 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 (is_tmpl_parm && i < nargs)
        {
          /* 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.  Note that ARG can also be a TREE_LIST
             in other cases such as overloaded functions.  */
          if (arg != NULL_TREE && arg != error_mark_node)
            arg = TREE_VALUE (arg);
        }

      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;
        }

      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);

      if (is_tmpl_parm && i < nargs)
        is_type = TREE_CODE (arg) == TYPE_DECL || is_tmpl_type;
      else
        is_type = TREE_CODE_CLASS (TREE_CODE (arg)) == 't' || is_tmpl_type;

      if (requires_type && ! is_type && TREE_CODE (arg) == SCOPE_REF
          && TREE_CODE (TREE_OPERAND (arg, 0)) == TEMPLATE_TYPE_PARM)
        {
          cp_pedwarn ("to refer to a type member of a template parameter,");
          cp_pedwarn ("  use `typename %E'", arg);

          arg = make_typename_type (TREE_OPERAND (arg, 0),
                                    TREE_OPERAND (arg, 1));
          is_type = 1;
        }
      if (is_type != requires_type)
        {
          if (in_decl)
            {
              if (complain)
                {
                  cp_error ("type/value mismatch at argument %d in template parameter list for `%D'",
                            i + 1, in_decl);
                  if (is_type)
                    cp_error ("  expected a constant of type `%T', got `%T'",
                              TREE_TYPE (parm),
                              (is_tmpl_type ? DECL_NAME (arg) : arg));
                  else
                    cp_error ("  expected a type, got `%E'", arg);
                }
            }
          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, 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, 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;
}

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

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_real (ctx, 0, 1);
      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_real (arg, 0, 1));
          continue;
        }
      else if (TREE_CODE (parm) == TEMPLATE_DECL)
        {
          if (TREE_CODE (arg) == TEMPLATE_DECL)
            /* Already substituted with real template.  Just output 
               the template name here */
            cat (IDENTIFIER_POINTER (DECL_NAME (arg)));
          else
            /* Output the parameter declaration */
            cat (type_as_string_real (arg, 0, 1));
          continue;
        }
      else
        my_friendly_assert (TREE_CODE (parm) == PARM_DECL, 269);

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

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

#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;
{
  tree t;

  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);  
}

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

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

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

   D1 is the PTYPENAME terminal, and ARGLIST is the list of arguments.
   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 = 
            maybe_get_template_decl_from_type_decl
            (IDENTIFIER_CLASS_VALUE (d1));
          if (template == NULL_TREE)
            template = IDENTIFIER_NAMESPACE_VALUE (d1);
        }
      if (template)
        context = DECL_CONTEXT (template);
    }
  else if (TREE_CODE (d1) == TYPE_DECL && IS_AGGR_TYPE (TREE_TYPE (d1)))
    {
      if (CLASSTYPE_TEMPLATE_INFO (TREE_TYPE (d1)) == 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 if (TREE_CODE (d1) == TEMPLATE_DECL
           && TREE_CODE (DECL_RESULT (d1)) == TYPE_DECL)
    {
      template = d1;
      d1 = DECL_NAME (template);
      context = DECL_CONTEXT (template);
    }
  else
    my_friendly_abort (272);

  /* With something like `template <class T> class X class X { ... };'
     we could end up with D1 having nothing but an IDENTIFIER_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, 0);
      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, 0);
      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;
            }
        }

      /* FIXME avoid duplication.  */
      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, 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;

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

int
for_each_template_parm (t, fn, data)
     tree t;
     tree_fn_t fn;
     void* data;
{
  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 for_each_template_parm (TREE_TYPE (t), fn, data);

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

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

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

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

    case TEMPLATE_DECL:
      /* A template template parameter is encountered */
      if (DECL_TEMPLATE_TEMPLATE_PARM_P (t))
        /* We are parsing a template declaration */
        return 1;
      /* We are instantiating templates with template template
         parameter */
      return 0;
      
    case CONST_DECL:
      if (for_each_template_parm (DECL_INITIAL (t), fn, data))
        return 1;
      goto check_type_and_context;

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

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

      /* template parm nodes */
    case TEMPLATE_TYPE_PARM:
    case TEMPLATE_TEMPLATE_PARM:
    case TEMPLATE_PARM_INDEX:
      if (fn)
        return (*fn)(t, data);
      else
        return 1;

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

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

    case ENUMERAL_TYPE:
      {
        tree v;

        for (v = TYPE_VALUES (t); v != NULL_TREE; v = TREE_CHAIN (v))
          if (for_each_template_parm (TREE_VALUE (v), fn, data))
            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 for_each_template_parm (TREE_OPERAND (t, 0), fn, data);

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

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

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

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

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

static struct tinst_level *current_tinst_level = 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

/* Print out all the template instantiations that we are currently
   working on.  */

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

  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;
}

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

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

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

      print_template_context ();

      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;
}


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

   Returns an appropriate tsbust'd friend declaration.  */

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

      template_id
        = lookup_template_function (tsubst_expr (DECL_TI_TEMPLATE (decl),
                                                 args, NULL_TREE),
                                    tsubst (DECL_TI_ARGS (decl),
                                            args, NULL_TREE));
      
      /* Temporarily remove the DECL_TEMPLATE_INFO so as not to
         confuse tsubst.  */
      tinfo = DECL_TEMPLATE_INFO (decl);
      DECL_TEMPLATE_INFO (decl) = NULL_TREE;
      new_friend = tsubst (decl, args, NULL_TREE);
      DECL_TEMPLATE_INFO (decl) = tinfo;

      tmpl = determine_specialization (template_id,
                                       new_friend,
                                       &new_args,
                                       0, 1);
      return instantiate_template (tmpl, new_args);
    }
    else
      new_friend = tsubst (decl, args, NULL_TREE);
        
  /* The new_friend will look like an instantiation, to the
     compiler, but is not an instantiation from the point of view of
     the language.  For example, we might have had:
     
     template <class T> struct S {
       template <class U> friend void f(T, U);
     };
     
     Then, in S<int>, template <class U> void f(int, U) is not an
     instantiation of anything.  */
  DECL_USE_TEMPLATE (new_friend) = 0;
  if (TREE_CODE (decl) == TEMPLATE_DECL)
    DECL_USE_TEMPLATE (DECL_TEMPLATE_RESULT (new_friend)) = 0;
  
  if (DECL_CONTEXT (new_friend) == NULL_TREE)
    {
      if (TREE_CODE (new_friend) == TEMPLATE_DECL)
        /* This declaration is a `primary' template.  */
        TREE_TYPE (DECL_INNERMOST_TEMPLATE_PARMS (new_friend))
            = new_friend;

        new_friend = pushdecl_top_level (new_friend);
    }
  else if (TYPE_SIZE (DECL_CONTEXT (new_friend)))
    {
      /* Check to see that the declaration is really present, and,
         possibly obtain an improved declaration.  */
      tree fn = check_classfn (DECL_CONTEXT (new_friend),
                               new_friend);
      
      if (fn)
        new_friend = fn;
    }

  return new_friend;
}


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

  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);

  if (DECL_TEMPLATE_INFO (template))
    {
      outer_args = DECL_TI_ARGS (template);
      while (DECL_TEMPLATE_INFO (template))
        template = DECL_TI_TEMPLATE (template);
    }
  else
    outer_args = NULL_TREE;

  t = most_specialized_class
    (DECL_TEMPLATE_SPECIALIZATIONS (template), args, outer_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, outer_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, outer_args);

  if (pedantic && uses_template_parms (args))
    /* If there are still template parameters amongst the args, then
       we can't instantiate the type; there's no telling whether or not one
       of the template parameters might eventually be instantiated to some
       value that results in a specialization being used.  */
    return type;

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

  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 (outer_args)
    args = add_to_template_args (outer_args, args);

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

  TYPE_HAS_CONSTRUCTOR (type) = TYPE_HAS_CONSTRUCTOR (pattern);
  TYPE_HAS_DESTRUCTOR (type) = TYPE_HAS_DESTRUCTOR (pattern);
  TYPE_HAS_ASSIGNMENT (type) = TYPE_HAS_ASSIGNMENT (pattern);
  TYPE_OVERLOADS_CALL_EXPR (type) = TYPE_OVERLOADS_CALL_EXPR (pattern);
  TYPE_OVERLOADS_ARRAY_REF (type) = TYPE_OVERLOADS_ARRAY_REF (pattern);
  TYPE_OVERLOADS_ARROW (type) = TYPE_OVERLOADS_ARROW (pattern);
  TYPE_GETS_NEW (type) = TYPE_GETS_NEW (pattern);
  TYPE_GETS_DELETE (type) = TYPE_GETS_DELETE (pattern);
  TYPE_VEC_DELETE_TAKES_SIZE (type) = TYPE_VEC_DELETE_TAKES_SIZE (pattern);
  TYPE_HAS_ASSIGN_REF (type) = TYPE_HAS_ASSIGN_REF (pattern);
  TYPE_HAS_CONST_ASSIGN_REF (type) = TYPE_HAS_CONST_ASSIGN_REF (pattern);
  TYPE_HAS_ABSTRACT_ASSIGN_REF (type) = TYPE_HAS_ABSTRACT_ASSIGN_REF (pattern);
  TYPE_HAS_INIT_REF (type) = TYPE_HAS_INIT_REF (pattern);
  TYPE_HAS_CONST_INIT_REF (type) = TYPE_HAS_CONST_INIT_REF (pattern);
  TYPE_HAS_DEFAULT_CONSTRUCTOR (type) = TYPE_HAS_DEFAULT_CONSTRUCTOR (pattern);
  TYPE_HAS_CONVERSION (type) = TYPE_HAS_CONVERSION (pattern);
  TYPE_USES_COMPLEX_INHERITANCE (type)
    = TYPE_USES_COMPLEX_INHERITANCE (pattern);
  TYPE_USES_MULTIPLE_INHERITANCE (type)
    = TYPE_USES_MULTIPLE_INHERITANCE (pattern);
  TYPE_USES_VIRTUAL_BASECLASSES (type)
    = TYPE_USES_VIRTUAL_BASECLASSES (pattern);
  TYPE_PACKED (type) = TYPE_PACKED (pattern);
  TYPE_ALIGN (type) = TYPE_ALIGN (pattern);

  CLASSTYPE_LOCAL_TYPEDECLS (type) = CLASSTYPE_LOCAL_TYPEDECLS (pattern);

  /* If this is a partial instantiation, don't tsubst anything.  We will
     only use this type for implicit typename, so the actual contents don't
     matter.  All that matters is whether a particular name is a type.  */
  if (uses_template_parms (type))
    {
      TYPE_BINFO_BASETYPES (type) = TYPE_BINFO_BASETYPES (pattern);
      TYPE_FIELDS (type) = TYPE_FIELDS (pattern);
      TYPE_METHODS (type) = TYPE_METHODS (pattern);
      CLASSTYPE_TAGS (type) = CLASSTYPE_TAGS (pattern);
      TYPE_SIZE (type) = integer_zero_node;
      goto end;
    }

  {
    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, 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 (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;
      }
  }

  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)
        {
          (void) tsubst_enum (tag, args, field_chain);
          while (*field_chain)
            {
              DECL_FIELD_CONTEXT (*field_chain) = type;
              field_chain = &TREE_CHAIN (*field_chain);
            }
        }
      else
        tsubst (tag, 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, NULL_TREE);
        if (TREE_CODE (r) == VAR_DECL)
          {
            pending_statics = perm_tree_cons (NULL_TREE, r, pending_statics);
            /* Perhaps we should do more of grokfield here.  */
            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);
    }

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

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

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

            }
        }
    }

  t = CLASSTYPE_FRIEND_CLASSES (type)
    = tsubst (CLASSTYPE_FRIEND_CLASSES (pattern), args, NULL_TREE);

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

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

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

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

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

  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));

 end:
  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;
}

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

   If is_spec, then we are dealing with a specialization of a member
   template, and want the second-innermost args, the innermost ones that
   are instantiated.  */

tree
innermost_args (args, is_spec)
     tree args;
     int is_spec;
{
  if (TREE_CODE (TREE_VEC_ELT (args, 0)) == TREE_VEC)
    return TREE_VEC_ELT (args, TREE_VEC_LENGTH (args) - 1 - is_spec);
  return args;
}

/* Take the tree structure T and replace template parameters used therein
   with the argument vector ARGS.  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, in_decl)
     tree t, args;
     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
      && TREE_CODE (t) != TEMPLATE_DECL)
    type = tsubst (type, args, 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, 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, in_decl);
          tree context;
          tree r;

          context = 
            TYPE_CONTEXT (t) 
            ? tsubst (TYPE_CONTEXT (t), args, 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, 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, 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_PARM_INDEX:
      {
        int idx;
        int level;
        int levels;
        tree r = NULL_TREE;

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

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

            if (TREE_VEC_ELT (args, 0) != NULL_TREE
                && TREE_CODE (TREE_VEC_ELT (args, 0)) == TREE_VEC)
              {
                levels = TREE_VEC_LENGTH (args);
                if (level <= levels)
                  arg = TREE_VEC_ELT
                    (TREE_VEC_ELT (args, level - 1), idx);
              }
            else
              {
                levels = 1;
                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, 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 (level == 1)
          /* This can happen during the attempted tsubst'ing in
             unify.  This means that we don't yet have any information
             about the template parameter in question.  */
          return t;

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

            if (TREE_CODE (t) == TEMPLATE_TEMPLATE_PARM
                && CLASSTYPE_TEMPLATE_INFO (t))
              {
                tree argvec = tsubst (CLASSTYPE_TI_ARGS (t), args, in_decl);
                CLASSTYPE_TEMPLATE_INFO (r)
                  = perm_tree_cons (TYPE_NAME (t), argvec, NULL_TREE);
              }
            break;

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

        return r;
      }

    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 parms;
        tree* new_parms;
        tree spec;
        int is_template_template_parm = DECL_TEMPLATE_TEMPLATE_PARM_P (t);

        if (!is_template_template_parm)
          {
            /* We might already have an instance of this template. */
            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;

        if (is_template_template_parm)
          {
            tree new_decl = tsubst (decl, args, in_decl);
            DECL_RESULT (tmpl) = new_decl;
            TREE_TYPE (tmpl) = TREE_TYPE (new_decl);
            return tmpl;
          }

        DECL_CONTEXT (tmpl) = tsubst (DECL_CONTEXT (t),
                                      args, in_decl);
        DECL_CLASS_CONTEXT (tmpl) = tsubst (DECL_CLASS_CONTEXT (t),
                                            args, in_decl);
        DECL_TEMPLATE_INFO (tmpl) = build_tree_list (t, args);

        if (TREE_CODE (decl) == TYPE_DECL)
          {
            tree new_type = tsubst (TREE_TYPE (t), args, in_decl);
            TREE_TYPE (tmpl) = new_type;
            CLASSTYPE_TI_TEMPLATE (new_type) = tmpl;
            DECL_RESULT (tmpl) = TYPE_MAIN_DECL (new_type);
          }
        else
          {
            tree new_decl = tsubst (decl, args, 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. */
        for (new_parms = &DECL_TEMPLATE_PARMS (tmpl),
               parms = DECL_TEMPLATE_PARMS (t);
             TREE_CHAIN (parms) != NULL_TREE;
             new_parms = &(TREE_CHAIN (*new_parms)),
               parms = TREE_CHAIN (parms))
          {
            tree new_vec = 
              make_tree_vec (TREE_VEC_LENGTH (TREE_VALUE (parms)));
            int i;

            for (i = 0; i < TREE_VEC_LENGTH (new_vec); ++i)
              {
                tree default_value =
                  TREE_PURPOSE (TREE_VEC_ELT (TREE_VALUE (parms), i));
                tree parm_decl = 
                  TREE_VALUE (TREE_VEC_ELT (TREE_VALUE (parms), i));
                  
                TREE_VEC_ELT (new_vec, i)
                  = build_tree_list (tsubst (default_value, args, in_decl),
                                     tsubst (parm_decl, args, in_decl));
                  
              }

            *new_parms = 
              tree_cons (build_int_2 (0, 
                                      TREE_INT_CST_HIGH 
                                      (TREE_PURPOSE (parms)) - 1),
                         new_vec,
                         NULL_TREE);
          }

        if (PRIMARY_TEMPLATE_P (t))
          TREE_TYPE (DECL_INNERMOST_TEMPLATE_PARMS (tmpl)) = tmpl;

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

        /* 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,
                                in_decl); 
            new_fn = tsubst (DECL_RESULT (fn), args,
                             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;
        tree argvec;
        tree tmpl = NULL_TREE;
        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, t);
            type = tsubst (type, args, in_decl);
          }
        else
          {
            member = 0;
            ctx = NULL_TREE;
            type = tsubst (type, args, in_decl);
          }

        /* If we are instantiating a specialization, get the other args.  */
        if (DECL_TEMPLATE_INFO (t) != NULL_TREE)
          {
            tree spec;

            tmpl = DECL_TI_TEMPLATE (t);

            /* Start by getting the innermost args.  */
            argvec = tsubst (DECL_TI_ARGS (t), args, in_decl);

            if (DECL_TEMPLATE_INFO (tmpl))
              argvec = complete_template_args (tmpl, argvec, 0);

            /* Do we already have this instantiation?  */
            spec = retrieve_specialization (tmpl, argvec);
            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, 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 function 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
              {
                tree tparms; 
                tree targs;

                if (!DECL_TEMPLATE_SPECIALIZATION (tmpl)) 
                  {
                    /* 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.  Levels of parms that have been bound
                       before are not represented in DECL_TEMPLATE_PARMS.  */
                    tparms = DECL_TEMPLATE_PARMS (tmpl);
                    while (tparms && TREE_CHAIN (tparms) != NULL_TREE)
                      tparms = TREE_CHAIN (tparms);
                    
                    targs = innermost_args (args, 0);
                  }
                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, 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;
        DECL_PENDING_INLINE_INFO (r) = 0;
        TREE_USED (r) = 0;

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

        if (DECL_TEMPLATE_INFO (t) != NULL_TREE)
          {
            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;
        if (TREE_CODE (DECL_INITIAL (r)) != TEMPLATE_PARM_INDEX)
          DECL_INITIAL (r) = TREE_TYPE (r);
        else
          DECL_INITIAL (r) = tsubst (DECL_INITIAL (r), args, in_decl);

        DECL_CONTEXT (r) = NULL_TREE;
#ifdef PROMOTE_PROTOTYPES
        if ((TREE_CODE (type) == INTEGER_TYPE
             || TREE_CODE (type) == ENUMERAL_TYPE)
            && TYPE_PRECISION (type) < TYPE_PRECISION (integer_type_node))
          DECL_ARG_TYPE (r) = integer_type_node;
#endif
        if (TREE_CHAIN (t))
          TREE_CHAIN (r) = tsubst (TREE_CHAIN (t), args, 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, in_decl);
#endif
        DECL_INITIAL (r) = tsubst_expr (DECL_INITIAL (t), args, 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, in_decl);
        TREE_CHAIN (r) = NULL_TREE;
        return r;
      }

    case VAR_DECL:
      {
        tree r;
        tree ctx = tsubst_copy (DECL_CONTEXT (t), args, 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, 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, in_decl);
        value = TREE_VALUE (t);
        if (value)
          value = tsubst (value, args, in_decl);
        chain = TREE_CHAIN (t);
        if (chain && chain != void_type_node)
          chain = tsubst (chain, args, 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, 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, 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, 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, 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, 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, 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, in_decl);
            fntype = build_exception_variant (fntype, raises);
          }
        return fntype;
      }
    case ARRAY_TYPE:
      {
        tree domain = tsubst (TYPE_DOMAIN (t), args, 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, in_decl),
                          tsubst (TREE_OPERAND (t, 1), args, in_decl)));

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

    case TYPENAME_TYPE:
      {
        tree ctx = tsubst (TYPE_CONTEXT (t), args, in_decl);
        tree f = tsubst_copy (TYPENAME_TYPE_FULLNAME (t), args, in_decl);
        f = make_typename_type (ctx, f);
        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, in_decl));
      
    case ADDR_EXPR:
      return make_reference_declarator
        (type, tsubst (TREE_OPERAND (t, 0), args, in_decl));

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

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

    case SCOPE_REF:
      return build_parse_node
        (TREE_CODE (t), tsubst (TREE_OPERAND (t, 0), args, in_decl),
         tsubst (TREE_OPERAND (t, 1), args, 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, in_decl)
     tree t, args;
     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;
          if (TREE_CODE (DECL_CONTEXT (t)) == FUNCTION_DECL)
            return lookup_name (DECL_NAME (t), 0);

          ctx = tsubst (DECL_CONTEXT (t), args, in_decl);
          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, in_decl);
      mark_used (t);
      return t;

    case TEMPLATE_DECL:
      if (is_member_template (t))
        return tsubst (t, args, 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, in_decl),
         tsubst_copy (TREE_OPERAND (t, 0), args, 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, 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, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, in_decl));

    case CALL_EXPR:
      {
        tree fn = TREE_OPERAND (t, 0);
        if (is_overloaded_fn (fn))
          fn = tsubst_copy (get_first_fn (fn), args, in_decl);
        else
          /* Sometimes FN is a LOOKUP_EXPR.  */
          fn = tsubst_copy (fn, args, in_decl);
        return build_nt
          (code, fn, tsubst_copy (TREE_OPERAND (t, 1), args, 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, in_decl);
            if (TREE_CODE (name) != IDENTIFIER_NODE)
              name = TYPE_MAIN_VARIANT (name);
            name = build1 (BIT_NOT_EXPR, NULL_TREE, name);
          }
        else if (TREE_CODE (name) == SCOPE_REF
                 && TREE_CODE (TREE_OPERAND (name, 1)) == BIT_NOT_EXPR)
          {
            tree base = tsubst_copy (TREE_OPERAND (name, 0), args, in_decl);
            name = TREE_OPERAND (name, 1);
            name = tsubst_copy (TREE_OPERAND (name, 0), args, in_decl);
            if (TREE_CODE (name) != IDENTIFIER_NODE)
              name = TYPE_MAIN_VARIANT (name);
            name = build1 (BIT_NOT_EXPR, NULL_TREE, name);
            name = build_nt (SCOPE_REF, base, name);
          }
        else
          name = tsubst_copy (TREE_OPERAND (t, 0), args, in_decl);
        return build_nt
          (code, name, tsubst_copy (TREE_OPERAND (t, 1), args, in_decl),
           tsubst_copy (TREE_OPERAND (t, 2), args, 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, in_decl),
           tsubst_copy (TREE_OPERAND (t, 1), args, in_decl),
           tsubst_copy (TREE_OPERAND (t, 2), args, in_decl));

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

        return r;
      }

    case NEW_EXPR:
      {
        tree r = build_nt
        (code, tsubst_copy (TREE_OPERAND (t, 0), args, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, in_decl),
         tsubst_copy (TREE_OPERAND (t, 2), args, 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, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, 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, 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, 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, in_decl);
        value = TREE_VALUE (t);
        if (value)
          value = tsubst_copy (value, args, in_decl);
        chain = TREE_CHAIN (t);
        if (chain && chain != void_type_node)
          chain = tsubst_copy (chain, args, in_decl);
        if (purpose == TREE_PURPOSE (t)
            && value == TREE_VALUE (t)
            && chain == TREE_CHAIN (t))
          return t;
        return tree_cons (purpose, value, chain);
      }

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

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

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

    default:
      return t;
    }
}

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

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

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

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

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

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

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

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

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

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

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

    case IF_STMT:
      {
        tree tmp;

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

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

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

        finish_if_stmt ();
      }
      break;

    case COMPOUND_STMT:
      {
        tree substmt;

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

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

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

    case SWITCH_STMT:
      {
        tree val, tmp;

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

        finish_switch_stmt (val, NULL_TREE);
      }
      break;

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

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

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

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

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

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

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

    default:
      return build_expr_from_tree (tsubst_copy (t, args, 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);

  /* FIXME this won't work with member templates; we only have one level
     of args here.  */
  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);

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

  /* We allow incomplete unification without an error message here
     because the standard doesn't seem to explicitly prohibit it.  Our
     callers must be ready to deal with unification failures in any
     event.  */
  i = type_unification (DECL_INNERMOST_TEMPLATE_PARMS (fn), 
                        targs,
                        fn_arg_types,
                        decl_arg_types,
                        explicit_targs,
                        strict, 1);

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

  for (i = 0; i < ntparms; i++)
    TREE_VEC_ELT (targs, i) = NULL_TREE;

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

      if (arg_vec == error_mark_node)
        return 1;

      explicit_mask = alloca (sizeof (int) * TREE_VEC_LENGTH (targs));
      bzero (explicit_mask, sizeof(int) * TREE_VEC_LENGTH (targs));

      for (i = 0; 
           i < TREE_VEC_LENGTH (arg_vec) 
             && TREE_VEC_ELT (arg_vec, i) != NULL_TREE;  
           ++i)
        {
          TREE_VEC_ELT (targs, i) = TREE_VEC_ELT (arg_vec, i);
          /* Let unify know that this argument was explicit.  */
          explicit_mask [i] = 1;
        }
    }
  else
    explicit_mask = 0;

  r = type_unification_real (tparms, targs, parms, args, 0,
                             strict, allow_incomplete, explicit_mask); 

  return r;
}

/* Like type_unfication.  EXPLICIT_MASK, if non-NULL, is an array of
   integers, with ones in positions corresponding to arguments in
   targs that were provided explicitly, and zeros elsewhere.  */

static int
type_unification_real (tparms, targs, parms, args, subr,
                       strict, allow_incomplete, explicit_mask)
     tree tparms, targs, parms, args;
     int subr, strict, allow_incomplete;
     int* explicit_mask;
{
  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 ntparms;
              tree targs;

              /* Have to back unify here */
              arg = TREE_VALUE (arg);
              ntparms = DECL_NTPARMS (arg);
              targs = make_scratch_vec (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, 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, strict,
                     explicit_mask)) 
        {
        case 0:
          break;
        case 1:
          return 1;
        }
    }
  /* Fail if we've reached the end of the parm list, and more args
     are present, and the parm list isn't variadic.  */
  if (args && args != void_list_node && parms == void_list_node)
    return 1;
  /* Fail if parms are left and they don't have default values.  */
  if (parms
      && parms != void_list_node
      && TREE_PURPOSE (parms) == NULL_TREE)
    return 1;
  if (!subr)
    for (i = 0; i < ntparms; i++)
      if (TREE_VEC_ELT (targs, i) == NULL_TREE)
        {
          if (!allow_incomplete)
            error ("incomplete type unification");
          return 2;
        }
  return 0;
}

/* Returns the level of DECL, which declares a template parameter.  */

int
template_decl_level (decl)
     tree decl;
{
  switch (TREE_CODE (decl))
    {
    case TYPE_DECL:
    case TEMPLATE_DECL:
      return TEMPLATE_TYPE_LEVEL (TREE_TYPE (decl));

    case PARM_DECL:
      return TEMPLATE_PARM_LEVEL (DECL_INITIAL (decl));

    default:
      my_friendly_abort (0);
      return 0;
    }
}

/* Tail recursion is your friend.  */

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

  /* I don't think this will do the right thing with respect to types.
     But the only case I've seen it in so far has been array bounds, where
     signedness is the only information lost, and I think that will be
     okay.  */
  while (TREE_CODE (parm) == NOP_EXPR)
    parm = TREE_OPERAND (parm, 0);

  if (arg == error_mark_node)
    return 1;
  if (arg == unknown_type_node)
    return 1;
  /* If PARM uses template parameters, then we can't bail out here,
     even in ARG == PARM, since we won't record unifications for the
     template parameters.  We might need them if we're trying to
     figure out which of two things is more specialized.  */
  if (arg == parm && !uses_template_parms (parm))
    return 0;

  /* We can't remove cv-quals when strict.  */
  if (strict && TREE_CODE (arg) == TREE_CODE (parm)
      && TREE_CODE_CLASS (TREE_CODE (arg)) == 't'
      && (TYPE_READONLY (arg) < TYPE_READONLY (parm)
          || TYPE_VOLATILE (arg) < TYPE_VOLATILE (parm)))
    return 1;

  switch (TREE_CODE (parm))
    {
    case TYPENAME_TYPE:
      /* In a type which contains a nested-name-specifier, template
         argument values cannot be deduced for template parameters used
         within the nested-name-specifier.  */
      return 0;

    case TEMPLATE_TYPE_PARM:
    case TEMPLATE_TEMPLATE_PARM:
      tparm = TREE_VALUE (TREE_VEC_ELT (tparms, 0));

      if (TEMPLATE_TYPE_LEVEL (parm)
          != template_decl_level (tparm))
        /* The PARM is not one we're trying to unify.  Just check
           to see if it matches ARG.  */
        return (TREE_CODE (arg) == TREE_CODE (parm)
                && comptypes (parm, arg, 1)) ? 0 : 1;
      idx = TEMPLATE_TYPE_IDX (parm);
      targ = TREE_VEC_ELT (targs, idx);
      tparm = TREE_VALUE (TREE_VEC_ELT (tparms, idx));

      /* Check for mixed types and values.  */
      if ((TREE_CODE (parm) == TEMPLATE_TYPE_PARM
           && TREE_CODE (tparm) != TYPE_DECL)
          || (TREE_CODE (parm) == TEMPLATE_TEMPLATE_PARM 
              && TREE_CODE (tparm) != TEMPLATE_DECL))
        return 1;

      if (!strict && targ != NULL_TREE 
          && explicit_mask && explicit_mask[idx])
        /* 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 (TREE_CODE (parm) == TEMPLATE_TEMPLATE_PARM)
        {
          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, 0)
                    == 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_PARM_INDEX)
                      continue;

                    /* This argument can be deduced.  */

                    if (unify (tparms, targs, ntparms, t, 
                               TREE_VEC_ELT (argvec, i), strict, explicit_mask))
                      return 1;
                  }
              }
              arg = CLASSTYPE_TI_TEMPLATE (arg);
            }
        }
      else
        {
          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 (targ != NULL_TREE 
          && (comptypes (targ, arg, 1)
              || (explicit_mask && explicit_mask[idx])))
        return 0;
      else if (targ)
        return 1;
      TREE_VEC_ELT (targs, idx) = arg;
      return 0;

    case TEMPLATE_PARM_INDEX:
      tparm = TREE_VALUE (TREE_VEC_ELT (tparms, 0));

      if (TEMPLATE_PARM_LEVEL (parm) 
          != template_decl_level (tparm))
        /* The PARM is not one we're trying to unify.  Just check
           to see if it matches ARG.  */
        return (TREE_CODE (arg) == TREE_CODE (parm)
                && cp_tree_equal (parm, arg)) ? 0 : 1;

      idx = TEMPLATE_PARM_IDX (parm);
      targ = TREE_VEC_ELT (targs, idx);

      if (targ)
        {
          int i = cp_tree_equal (targ, arg);
          if (i == 1)
            return 0;
          else if (i == 0)
            return 1;
          else
            my_friendly_abort (42);
        }

      TREE_VEC_ELT (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), strict, explicit_mask);

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

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

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

    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), strict, explicit_mask))
            return 1;
          if (TYPE_MAX_VALUE (parm) && TYPE_MAX_VALUE (arg)
              && unify (tparms, targs, ntparms, TYPE_MAX_VALUE (parm),
                        TYPE_MAX_VALUE (arg), strict, explicit_mask))
            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 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),
                     strict, explicit_mask))
            return 1;
        return 0;
      }

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

      /* 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 (! 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), strict, explicit_mask);
        }
      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), strict, explicit_mask))
        return 1;
      return type_unification_real (tparms, targs, TYPE_ARG_TYPES (parm),
                                    TYPE_ARG_TYPES (arg), 1, 
                                    strict, 0, explicit_mask);

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

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

    case TEMPLATE_DECL:
      /* Matched cases are handled by the ARG == PARM test above.  */
      return 1;

    default:
      if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (TREE_CODE (parm))))
        {
          /* We're looking at an expression.  This can happen with
             something like:

               template <int I>
               void foo(S<I>, S<I + 2>);

             If the call looked like:

               foo(S<2>(), S<4>());

             we would have already matched `I' with `2'.  Now, we'd
             like to know if `4' matches `I + 2'.  So, we substitute
             into that expression, and fold constants, in the hope of
             figuring it out.  */
          tree t = 
            maybe_fold_nontype_arg (tsubst_expr (parm, targs, NULL_TREE)); 
          enum tree_code tc = TREE_CODE (t);

          if (tc == MINUS_EXPR 
              && TREE_CODE (TREE_OPERAND (t, 0)) == TEMPLATE_PARM_INDEX
              && TREE_CODE (TREE_OPERAND (t, 1)) == INTEGER_CST)
            {
              /* We handle this case specially, since it comes up with
                 arrays.  In particular, something like:

                 template <int N> void f(int (&x)[N]);

                 Here, we are trying to unify the range type, which
                 looks like [0 ... (N - 1)].  */
              tree t1, t2;
              t1 = TREE_OPERAND (parm, 0);
              t2 = TREE_OPERAND (parm, 1);

              t = maybe_fold_nontype_arg (build (PLUS_EXPR,
                                                 integer_type_node,
                                                 arg, t2));

              return unify (tparms, targs, ntparms, t1, t,
                            strict, explicit_mask);
            }

          if (!IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (tc)))
            /* Good, we mangaged to simplify the exression.  */
            return unify (tparms, targs, ntparms, t, arg, strict,
                          explicit_mask);
          else
            /* Bad, we couldn't simplify this.  Assume it doesn't
               unify.  */
            return 1;
        }
      else
        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_overload (pat1, pat2, explicit_args);
  if (targs)
    {
      --winner;
    }

  targs = get_bindings_overload (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), NULL_TREE);
  if (targs)
    --winner;

  targs = get_class_bindings
    (TREE_VALUE (pat2), TREE_PURPOSE (pat2),
     TREE_PURPOSE (pat1), NULL_TREE);
  if (targs)
    ++winner;

  return winner;
}

/* Return the template arguments that will produce the function signature
   DECL from the function template FN, with the explicit template
   arguments EXPLICIT_ARGS.  If CHECK_RETTYPE is 1, the return type must
   also match.  */

static tree
get_bindings_real (fn, decl, explicit_args, check_rettype)
     tree fn, decl, explicit_args;
     int check_rettype;
{
  int ntparms = DECL_NTPARMS (fn);
  tree targs = make_scratch_vec (ntparms);
  tree decl_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)
    return NULL_TREE;

  if (check_rettype)
    {
      /* Check to see that the resulting return type is also OK.  */
      tree t = tsubst (TREE_TYPE (TREE_TYPE (fn)),
                       complete_template_args (fn, targs, 1),
                       NULL_TREE);

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

  return targs;
}

/* For most uses, we want to check the return type.  */

tree 
get_bindings (fn, decl, explicit_args)
     tree fn, decl, explicit_args;
{
  return get_bindings_real (fn, decl, explicit_args, 1);
}

/* But for more_specialized, we only care about the parameter types.  */

static tree
get_bindings_overload (fn, decl, explicit_args)
     tree fn, decl, explicit_args;
{
  return get_bindings_real (fn, decl, explicit_args, 0);
}

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

  if (outer_args)
    {
      tparms = tsubst (tparms, outer_args, NULL_TREE);
      parms = tsubst (parms, outer_args, NULL_TREE);
    }

  for (i = 0; i < TREE_VEC_LENGTH (parms); ++i)
    {
      switch (unify (tparms, vec, ntparms,
                     TREE_VEC_ELT (parms, i), TREE_VEC_ELT (args, i),
                     1, 0))
        {
        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, outer_args)
     tree specs, mainargs, outer_args;
{
  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, outer_args);
      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 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);
  }
}

/* Produce the definition of D, a _DECL generated from a template.  */

tree
instantiate_decl (d)
     tree d;
{
  tree ti = DECL_TEMPLATE_INFO (d);
  tree tmpl = TI_TEMPLATE (ti);
  tree args = TI_ARGS (ti);
  tree td, temp;
  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) 
         /* This next clause handles friend templates defined inside
            class templates.  The friend templates are not really
            instantiations from the point of view of the language, but
            they are instantiations from the point of view of the
            compiler.  */
         || (DECL_TEMPLATE_INFO (td) && !DECL_TEMPLATE_SPECIALIZATION (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,
                                      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;
  /* decl_pattern has all but one level of template parms bound.  Only pass
     in that one level of args.  */
  temp = innermost_args (args, DECL_TEMPLATE_SPECIALIZATION (decl_pattern));
  td = tsubst (decl_pattern, temp, 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,
                                       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, 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, 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, NULL_TREE);
      tree last = first;

      for (t = TREE_CHAIN (t); t; t = TREE_CHAIN (t))
        {
          tree x = tsubst (t, 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, NULL_TREE);
      tree val = tsubst_expr (TREE_VALUE (t), 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, field_chain)
     tree tag, args;
     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,
                                                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;
}