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"
#include "toplev.h"

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

extern struct obstack permanent_obstack;

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

tree current_template_parms;
HOST_WIDE_INT processing_template_decl;

tree pending_templates;
static tree *template_tail = &pending_templates;

tree maybe_templates;
static tree *maybe_template_tail = &maybe_templates;

int minimal_parse_mode;

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

static tree saved_trees;

#define obstack_chunk_alloc xmalloc
#define obstack_chunk_free free

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

static int unify PROTO((tree, tree, 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 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));
static tree tsubst_enum	PROTO((tree, tree, tree *));
static tree add_to_template_args PROTO((tree, tree));
static void maybe_adjust_types_for_deduction PROTO((unification_kind_t, tree*,
						    tree*)); 
static int  type_unification_real PROTO((tree, tree, tree, tree,
					 int, unification_kind_t, int, 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 tsubst_friend_class PROTO((tree, tree));
static tree get_bindings_real PROTO((tree, tree, tree, int));
static int template_decl_level PROTO((tree));
static tree maybe_get_template_decl_from_type_decl PROTO((tree));
static int check_cv_quals_for_unify PROTO((int, tree, tree));
static tree tsubst_template_arg_vector PROTO((tree, tree));
static void regenerate_decl_from_template PROTO((tree, tree));
static int is_member_template_class PROTO((tree));

/* Nonzero if ARGVEC contains multiple levels of template arguments.  */
#define TMPL_ARGS_HAVE_MULTIPLE_LEVELS(NODE) 		\
  (NODE != NULL_TREE 					\
   && TREE_CODE (NODE) == TREE_VEC 			\
   && TREE_VEC_LENGTH (NODE) > 0 			\
   && TREE_VEC_ELT (NODE, 0) != NULL_TREE               \
   && TREE_CODE (TREE_VEC_ELT (NODE, 0)) == TREE_VEC)

/* 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 
	 && TREE_CODE (type) != NAMESPACE_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;
}

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

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

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

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

/* Return a new template argument vector which contains all of ARGS
   for all outer templates TMPL 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;
  int extra_arg_depth;

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

  if (TMPL_ARGS_HAVE_MULTIPLE_LEVELS (extra_args))
    extra_arg_depth = TREE_VEC_LENGTH (extra_args);
  else
    extra_arg_depth = 1;

  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 (!TMPL_ARGS_HAVE_MULTIPLE_LEVELS (args))
	    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 + extra_arg_depth + (!!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 + extra_arg_depth);

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

      if (depth > skip)
	{
	  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);
		  }
	      }
	}
    }

  if (extra_arg_depth == 1)
    TREE_VEC_ELT (new_args, depth++) = extra_args;
  else
    for (i = 0; i < extra_arg_depth; ++i)
      TREE_VEC_ELT (new_args, depth++) = TREE_VEC_ELT (extra_args, i);

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

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

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

/* 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;
}

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

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

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

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

  return 0;
}

/* 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, targs_in;
  tree templates = NULL_TREE;
  tree fn;
  int i;

  *targs_out = NULL_TREE;

  if (template_id == error_mark_node)
    return error_mark_node;

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

  if (fns == error_mark_node)
    return error_mark_node;

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

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

      fn = OVL_CURRENT (fns);
      if (!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,
				DEDUCE_EXACT, 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_at ("template-id `%D' for `%+D' does not match any template declaration",
		       template_id, decl);
	  return error_mark_node;
	}
      return NULL_TREE;
    }
  else if (TREE_CHAIN (templates) != NULL_TREE) 
    {
    ambiguous:
      if (complain)
	{
	  cp_error_at ("ambiguous template specialization `%D' for `%+D'",
		       template_id, decl);
	  print_candidates (templates);
	  return error_mark_node;
	}
      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 (declarator == error_mark_node)
	return error_mark_node;

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

      if (ctype != NULL_TREE && TYPE_BEING_DEFINED (ctype))
	{
	  /* 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
	 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 && tmpl != error_mark_node)
	{
	  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, 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
	  && TREE_CODE (TREE_TYPE (parm)) != TYPENAME_TYPE)
	{
	  cp_error ("`%#T' is not a valid type for a template constant parameter",
		    TREE_TYPE (parm));
	  if (DECL_NAME (parm) == NULL_TREE)
	    error ("  a template type parameter must begin with `class' or `typename'");
	  TREE_TYPE (parm) = void_type_node;
	}
      else if (pedantic
	       && (TREE_CODE (TREE_TYPE (parm)) == REAL_TYPE
		   || TREE_CODE (TREE_TYPE (parm)) == COMPLEX_TYPE))
	cp_pedwarn ("`%T' is not a valid type for a template constant parameter",
		    TREE_TYPE (parm));
      if (TREE_PERMANENT (parm) == 0)
        {
	  parm = copy_node (parm);
	  TREE_PERMANENT (parm) = 1;
        }
      decl = build_decl (CONST_DECL, DECL_NAME (parm), TREE_TYPE (parm));
      DECL_INITIAL (parm) = DECL_INITIAL (decl) 
	= build_template_parm_index (idx, processing_template_decl,
				     processing_template_decl,
				     decl, TREE_TYPE (parm));
    }
  else
    {
      tree t;
      parm = TREE_VALUE (parm);
      
      if (parm && TREE_CODE (parm) == TEMPLATE_DECL)
	{
	  t = make_lang_type (TEMPLATE_TEMPLATE_PARM);
	  /* This is for distinguishing between real templates and template 
	     template parameters */
	  TREE_TYPE (parm) = t;
	  TREE_TYPE (DECL_TEMPLATE_RESULT (parm)) = t;
	  decl = parm;
	}
      else
	{
	  t = make_lang_type (TEMPLATE_TYPE_PARM);
	  /* parm is either IDENTIFIER_NODE or NULL_TREE */
	  decl = build_decl (TYPE_DECL, parm, t);
	}
        
      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;

  --processing_template_parmlist;

  return saved_parmlist;
}

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

void
end_template_decl ()
{
  reset_specialization ();

  if (! processing_template_decl)
    return;

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

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

/* 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.  

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

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

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

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

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

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

  /* For determining whether this is a primary template or not, we're really
     interested in the lexical context, not the true context.  */
  if (is_friend)
    /* For a TYPE_DECL, there is no DECL_CLASS_CONTEXT.  */
    info = TREE_CODE (decl) == FUNCTION_DECL 
      ? DECL_CLASS_CONTEXT (decl) : current_class_type;
  else
    info = ctx;

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

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

  /* 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)
	{
	  if (IS_AGGR_TYPE_CODE (TREE_CODE (TREE_TYPE (decl)))
	      && CLASSTYPE_TEMPLATE_INFO (TREE_TYPE (decl))
	      && CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl)))
	    tmpl = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl));
	  else
	    {
	      cp_error ("`%D' does not declare a template type", decl);
	      return decl;
	    }
	}
      else if (! DECL_TEMPLATE_INFO (decl))
	{
	  cp_error ("template definition of non-template `%#D'", decl);
	  return decl;
	}
      else
	tmpl = DECL_TI_TEMPLATE (decl);
      
      if (is_member_template (tmpl) || is_member_template_class (tmpl))
	{
	  if (DECL_FUNCTION_TEMPLATE_P (tmpl)
	      && DECL_TEMPLATE_INFO (decl) && DECL_TI_ARGS (decl) 
	      && DECL_TEMPLATE_SPECIALIZATION (decl))
	    {
	      tree new_tmpl;

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

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

	      register_specialization (new_tmpl, tmpl, args);
	      return decl;
	    }
	  
	  a = TREE_VEC_ELT (args, TREE_VEC_LENGTH (args) - 1);
	  t = DECL_INNERMOST_TEMPLATE_PARMS (tmpl);
	  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.  We don't do this
     for a non-template member function of a nested template class
     because there we will never get a `partial instantiation' of the
     function containing the outer arguments, and so we must save all
     of the arguments here.  */
  if (TREE_CODE (decl) != FUNCTION_DECL 
      || template_class_depth (ctx) <= 1
      || primary)
    args = innermost_args (args, 0);

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

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

  if (primary)
    DECL_PRIMARY_TEMPLATE (tmpl) = tmpl;

  info = perm_tree_cons (tmpl, args, NULL_TREE);

  if (TREE_CODE (decl) == TYPE_DECL && DECL_ARTIFICIAL (decl))
    {
      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);
}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  if (is_overloaded_fn (expr))
    /* OK for now.  We'll check that it has external linkage later.
       Check this first since if expr_type is the unknown_type_node
       we would otherwise complain below.  */
    ;
  else if (INTEGRAL_TYPE_P (expr_type) 
	   || TYPE_PTRMEM_P (expr_type) 
	   || TYPE_PTRMEMFUNC_P (expr_type)
	   /* The next two are g++ extensions.  */
	   || TREE_CODE (expr_type) == REAL_TYPE
	   || TREE_CODE (expr_type) == COMPLEX_TYPE)
    {
      if (! TREE_CONSTANT (expr))
	{
	non_constant:
	  cp_error ("non-constant `%E' cannot be used as template argument",
		    expr);
	  return NULL_TREE;
	}
    }
  else 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.  */
      expr = digest_init (type, expr, (tree*) 0);

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

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

      return expr;

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

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

	    fn = instantiate_type (type_pointed_to, fns, 0);

	    if (fn == error_mark_node)
	      return error_mark_node;

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

	    expr = build_unary_op (ADDR_EXPR, fn, 0);

	    my_friendly_assert (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;

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

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

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

	if (TREE_CODE (expr) == CONSTRUCTOR)
	  {
	    /* A ptr-to-member constant.  */
	    if (!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;
}

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

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

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

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

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

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

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

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

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

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

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

	case TEMPLATE_DECL:
	  /* We encounter instantiations of templates like
	       template <template <template <class> class> class TT>
	       class C;  */
	  sorry ("nested template template parameter");
	  return 0;

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

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

   If REQUIRE_ALL_ARGUMENTS is non-zero, all arguments must be
   provided in ARGLIST, or else trailing parameters must have default
   values.  If REQUIRE_ALL_ARGUMENTS is zero, we will attempt argument
   deduction for any unspecified trailing arguments.  */
   
static tree
coerce_template_parms (parms, arglist, in_decl,
		       complain,
		       require_all_arguments)
     tree parms, arglist;
     tree in_decl;
     int complain;
     int require_all_arguments;
{
  int nparms, nargs, i, lost = 0;
  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 && TREE_CODE (arglist) == TREE_LIST)
	    {
	      arg = arglist;
	      arglist = TREE_CHAIN (arglist);

	      if (arg == error_mark_node)
		lost++;
	      else
		arg = TREE_VALUE (arg);
	    }
	  else if (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 (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.
         This is necessary to handle the case where we pass a template name
         to a template template parameter in a scope where we've derived from
         in instantiation of that template, so the template name refers to that
         instantiation.  We really ought to handle this better.  */
      is_tmpl_type = (TREE_CODE (arg) == TEMPLATE_DECL
		      && TREE_CODE (DECL_TEMPLATE_RESULT (arg)) == TYPE_DECL)
		     || (TREE_CODE (arg) == TEMPLATE_TEMPLATE_PARM
			 && !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
			 && current_class_type
			 /* FIXME what about nested types?  */
			 && get_binfo (arg, current_class_type, 0));
      if (is_tmpl_type && TREE_CODE (arg) == TEMPLATE_TEMPLATE_PARM)
	arg = TYPE_STUB_DECL (arg);
      else if (is_tmpl_type && TREE_CODE (arg) == RECORD_TYPE)
	arg = CLASSTYPE_TI_TEMPLATE (arg);

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

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

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

	      if (coerce_template_template_parms (parmparm, argparm, 
						  in_decl, vec))
		{
		  val = arg;

		  /* TEMPLATE_TEMPLATE_PARM node is preferred over 
		     TEMPLATE_DECL.  */
		  if (val != error_mark_node 
		      && DECL_TEMPLATE_TEMPLATE_PARM_P (val))
		    val = TREE_TYPE (val);
		}
	      else
		{
		  if (in_decl && complain)
		    {
		      cp_error ("type/value mismatch at argument %d in template parameter list for `%D'",
				i + 1, in_decl);
		      cp_error ("  expected a template of type `%D', got `%D'", parm, arg);
		    }

		  val = error_mark_node;
		}
	    }
	  else
	    {
	      val = groktypename (arg);
	      if (! processing_template_decl)
		{
		  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.  */

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 && ctx != global_namespace)
    {
      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 if (TREE_CODE (ctx) == NAMESPACE_DECL)
	s = decl_as_string (ctx, 0);
      else
	my_friendly_abort (0);
      cat (s);
      cat ("::");
    }
  cat (name);
  ccat ('<');
  nparms = TREE_VEC_LENGTH (parms);
  my_friendly_assert (nparms == TREE_VEC_LENGTH (arglist), 268);
  for (i = 0; i < nparms; i++)
    {
      tree parm = TREE_VALUE (TREE_VEC_ELT (parms, i));
      tree arg = TREE_VEC_ELT (arglist, i);

      if (i)
	ccat (',');

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

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

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

#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));
      /* We do not pass in the context here since that is only needed
	 when mangling the name of instantiations, not the primary
	 template declaration.  In reality, it should not be needed
	 then either, but the way lookup_template_class operates
	 requires the context for the moment.  In the long run,
	 lookup_template_class should not be looking for existing
	 instantiations by matching mangled names, but rather by
	 matching the templates, and then scanning the instantiation
	 list.  */
      char *mangled_name = mangle_class_name_for_template
	(IDENTIFIER_POINTER (name),
	 DECL_INNERMOST_TEMPLATE_PARMS (CLASSTYPE_TI_TEMPLATE (t)),
	 CLASSTYPE_TI_ARGS (t), NULL_TREE);
      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
    (build_srcloc_here (), d, NULL_TREE);
  template_tail = &TREE_CHAIN (*template_tail);
  TI_PENDING_TEMPLATE_FLAG (ti) = 1;
}


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

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

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

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

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

  return build_min (TEMPLATE_ID_EXPR, type, fns, arglist);  
}

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

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
	{
	  if (context)
	    push_decl_namespace (context);
	  if (current_class_type != NULL_TREE)
	    template = 
	      maybe_get_template_decl_from_type_decl
	      (IDENTIFIER_CLASS_VALUE (d1));
	  if (template == NULL_TREE)
	    template = lookup_name_nonclass (d1);
	  if (context)
	    pop_decl_namespace ();
	}
      if (template)
	context = DECL_CONTEXT (template);
    }
  else if (TREE_CODE (d1) == TYPE_DECL && IS_AGGR_TYPE (TREE_TYPE (d1)))
    {
      if (CLASSTYPE_TEMPLATE_INFO (TREE_TYPE (d1)) == 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 (context == NULL_TREE)
    context = global_namespace;

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

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

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

      CLASSTYPE_GOT_SEMICOLON (parm) = 1;
      parmlist = DECL_INNERMOST_TEMPLATE_PARMS (template);

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

      arglist2 = copy_to_permanent (arglist2);
      CLASSTYPE_TEMPLATE_INFO (parm)
	= perm_tree_cons (template2, arglist2, NULL_TREE);
      TYPE_SIZE (parm) = 0;
      return parm;
    }
  else if (PRIMARY_TEMPLATE_P (template)
	   || (TREE_CODE (TYPE_CONTEXT (TREE_TYPE (template))) 
	       == FUNCTION_DECL))
    {
      tree arglist_for_mangling;

      parmlist = DECL_INNERMOST_TEMPLATE_PARMS (template);

      if (/* ARGLIST can be NULL_TREE if there are default arguments.  */
	  arglist != NULL_TREE
	  && TREE_CODE (arglist) == TREE_VEC 
	  && TREE_VEC_LENGTH (arglist) > 1
	  && list_length (DECL_TEMPLATE_PARMS (template)) > 1)
	{
	  /* We have multiple levels of arguments to coerce, at once.  */
	  tree new_args = 
	    make_tree_vec (list_length (DECL_TEMPLATE_PARMS (template)));
	  int i;
	  
	  for (i = TREE_VEC_LENGTH (arglist) - 1, 
		 t = DECL_TEMPLATE_PARMS (template); 
	       i >= 0 && t != NULL_TREE;
	       --i, t = TREE_CHAIN (t))
	    TREE_VEC_ELT (new_args, i) =
	      coerce_template_parms (TREE_VALUE (t),
				     TREE_VEC_ELT (arglist, i),
				     template, 1, 1);
	  arglist = new_args;
	}
      else
	arglist = coerce_template_parms (parmlist, 
					 innermost_args (arglist, 0),
					 template, 1, 1);
     if (arglist == error_mark_node)
	return error_mark_node;
      if (uses_template_parms (arglist))
	{
	  tree found;
	  if (comp_template_args
	      (CLASSTYPE_TI_ARGS (TREE_TYPE (template)), arglist))
	    found = TREE_TYPE (template);
	  else
	    {
	      for (found = DECL_TEMPLATE_INSTANTIATIONS (template);
		   found; found = TREE_CHAIN (found))
		{
		  if (TI_USES_TEMPLATE_PARMS (found)
		      && comp_template_args (TREE_PURPOSE (found), arglist))
		    break;
		}
	      if (found)
		found = TREE_VALUE (found);
	    }

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

      if (TREE_CODE (arglist) == TREE_VEC)
	arglist_for_mangling = innermost_args (arglist, 0);
      else
	arglist_for_mangling = arglist;

      /* FIXME avoid duplication.  */
      mangled_name = mangle_class_name_for_template (IDENTIFIER_POINTER (d1),
						     parmlist,
						     arglist_for_mangling,
						     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) = FROB_CONTEXT (context);
	  DECL_CONTEXT (type_decl) = FROB_CONTEXT (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);

      if (uses_template_parms (arglist))
	/* If the type makes use of template parameters, the
	   code that generates debugging information will crash.  */
	DECL_IGNORED_P (TYPE_STUB_DECL (t)) = 1;
    }

  return t;
}

/* 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;

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

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

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

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

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

      /* constructed type nodes */
    case POINTER_TYPE:
    case REFERENCE_TYPE:
      return for_each_template_parm (TREE_TYPE (t), fn, data);
    case RECORD_TYPE:
      if (TYPE_PTRMEMFUNC_FLAG (t))
	return for_each_template_parm (TYPE_PTRMEMFUNC_FN_TYPE (t),
				       fn, data);
    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))
	return for_each_template_parm (TREE_TYPE (t), fn, data);
      /* Already substituted template template parameter */
      return 0;
      
    case CONST_DECL:
      if (for_each_template_parm (DECL_INITIAL (t), fn, data))
	return 1;
      goto check_type_and_context;

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

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

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

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

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

    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 = first_rtl_op (TREE_CODE (t)); --i >= 0;)
	      if (for_each_template_parm (TREE_OPERAND (t, i), fn, data))
		return 1;
	    return 0;
	  }
	default:
	  break;
	}
      sorry ("testing %s for template parms",
	     tree_code_name [(int) TREE_CODE (t)]);
      my_friendly_abort (82);
      /* NOTREACHED */
      return 0;
    }
}

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

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

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

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

  if (err)
    {
      if (current_function_decl == p->decl)
	/* Avoid redundancy with the the "In function" line.  */;
      else if (current_function_decl == NULL_TREE)
	fprintf (stderr, "%s: In instantiation of `%s':\n",
		 file, decl_as_string (p->decl, 0));
      else
	my_friendly_abort (980521);

      if (p)
	{
	  line = p->line;
	  file = p->file;
	  p = p->next;
	}
    }

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

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

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

  last_template_error_tick = tinst_level_tick;
  print_template_context (1);
}

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

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

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

      print_template_context (0);

      return 0;
    }

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

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

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

  ++tinst_level_tick;
  return 1;
}

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

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

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

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

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

   Returns an appropriate tsbust'd friend declaration.  */

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

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

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

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

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

   Returns an appropriate tsbust'd friend type.  */

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

  tmpl = maybe_get_template_decl_from_type_decl (tmpl);

  if (tmpl != NULL_TREE && DECL_CLASS_TEMPLATE_P (tmpl))
    {
      /* The friend template has already been declared.  Just
	 check to see that the declarations match.  */
      redeclare_class_template (TREE_TYPE (tmpl),
				DECL_TEMPLATE_PARMS (friend_tmpl));
      friend_type = TREE_TYPE (tmpl);
    }
  else
    {
      /* The friend template has not already been declared.  In this
	 case, the instantiation of the template class will cause the
	 injection of this template into the global scope.  */
      tmpl = tsubst (friend_tmpl, args, NULL_TREE);

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

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

  return friend_type;
}

tree
instantiate_class_template (type)
     tree type;
{
  tree template, 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);
  TYPE_FOR_JAVA (type) = TYPE_FOR_JAVA (pattern); /* For libjava's JArray<T> */

  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, basetype;

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

	    basetype = TREE_TYPE (elt);

	    if (! IS_AGGR_TYPE (basetype))
	      cp_error
		("base type `%T' of `%T' fails to be a struct or class type",
		 basetype, type);
	    else if (TYPE_SIZE (complete_type (basetype)) == NULL_TREE)
	      cp_error ("base class `%T' of `%T' has incomplete type",
			basetype, type);

	    /* These are set up in xref_basetypes for normal classes, so
	       we have to handle them here for template bases.  */
	    if (TYPE_USES_VIRTUAL_BASECLASSES (basetype))
	      {
		TYPE_USES_VIRTUAL_BASECLASSES (type) = 1;
		TYPE_USES_COMPLEX_INHERITANCE (type) = 1;
	      }
	    TYPE_GETS_NEW (type) |= TYPE_GETS_NEW (basetype);
	    TYPE_GETS_DELETE (type) |= TYPE_GETS_DELETE (basetype);
	    CLASSTYPE_LOCAL_TYPEDECLS (type)
	      |= CLASSTYPE_LOCAL_TYPEDECLS (basetype);
	  }
	/* 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);

  /* 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)));

	    }
	}
    }

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

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

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

      make_friend_class (type, new_friend_type);

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

  /* This does injection for friend functions. */
  if (!processing_template_decl)
    {
      t = tsubst (DECL_TEMPLATE_INJECT (template), args, 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 (TMPL_ARGS_HAVE_MULTIPLE_LEVELS (args))
    return TREE_VEC_ELT (args, TREE_VEC_LENGTH (args) - 1 - is_spec);
  return args;
}

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

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

/* 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
      || TREE_CODE (t) == NAMESPACE_DECL)
    return t;

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

  if (type && TREE_CODE (t) != FUNCTION_DECL
      && TREE_CODE (t) != TYPENAME_TYPE
      && TREE_CODE (t) != TEMPLATE_DECL
      && TREE_CODE (t) != IDENTIFIER_NODE)
    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;

	  if (TYPE_CONTEXT (t) != NULL_TREE)
	    {
	      context = tsubst (TYPE_CONTEXT (t), args, in_decl);
	  
	      if (TREE_CODE (context) != FUNCTION_DECL
		  && TREE_CODE (context) != NAMESPACE_DECL)
		{
		  /* For a member class template, we need all the
		     template arguments.  */
		  if (CLASSTYPE_IS_TEMPLATE (TYPE_CONTEXT (t)))
		    argvec = 
		      add_to_template_args (CLASSTYPE_TI_ARGS (context),
					    argvec);

		  if (CLASSTYPE_TEMPLATE_INFO (context))
		    argvec = 
		      complete_template_args (CLASSTYPE_TI_TEMPLATE (context),
					      argvec, 0);
		}
	    }
	  else
	    context = 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:
    case NAMESPACE_DECL:
      return t;

    case ENUMERAL_TYPE:
      {
	tree ctx = tsubst (TYPE_CONTEXT (t), args, in_decl);
	if (ctx == NULL_TREE || TREE_CODE (ctx) == NAMESPACE_DECL)
	  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 (TMPL_ARGS_HAVE_MULTIPLE_LEVELS (args))
	      {
		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, type, 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);
	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))
	  DECL_PRIMARY_TEMPLATE (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_CLASS_SCOPE_P (t))
	  {
	    if (DECL_NAME (t) == constructor_name (DECL_CONTEXT (t)))
	      member = 2;
	    else
	      member = 1;
	    ctx = tsubst (DECL_CLASS_CONTEXT (t), args, t);
	  }
	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.  */
	    if (DECL_TEMPLATE_SPECIALIZATION (tmpl))
	      argvec = args;
	    else
	      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));
	  }

	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_PENDING_INLINE_INFO (r) = 0;
	TREE_USED (r) = 0;

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

	if (DECL_DESTRUCTOR_P (t))
	  DECL_ASSEMBLER_NAME (r) = build_destructor_name (ctx);
	else 
	  {
	    /* Instantiations of template functions must be mangled
	       specially, in order to conform to 14.5.5.1
	       [temp.over.link].  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 
		  (r, arg_types, TREE_TYPE (TREE_TYPE (tmpl)),
		   tparms, targs, member);
	      }
	  }
	DECL_RTL (r) = 0;
	make_decl_rtl (r, NULL_PTR, 1);

	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)
	  SET_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;
	if (TREE_CODE (type) == VOID_TYPE)
	  cp_error_at ("instantiation of `%D' as type void", r);
	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;
	if (TREE_CODE (type) == VOID_TYPE)
	  cp_error_at ("instantiation of `%D' as type void", r);
	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.  We always need to make a copy, of the node
	     itself and of its BINFO_BASETYPES.  */

	  t = copy_node (t);

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

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

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

    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) = FROB_CONTEXT (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, NULL_TREE);

    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);
	    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);
	    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;

  if (tmpl == error_mark_node)
    return error_mark_node;

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

  /* Check to see if we already have this specialization.  This does work
     for member template specializations; the list is set up from the
     tsubst TEMPLATE_DECL case when the containing class is instantiated.  */
  if (DECL_FUNCTION_TEMPLATE_P (tmpl))
    {
      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 FN is a TEMPLATE_DECL for a function.  The ARGS are the
   arguments that are being used when calling it.  

   If FN is a conversion operator, RETURN_TYPE is the type desired as
   the result of the conversion operator.

   The EXTRA_FN_ARG, if any, is the type of an additional
   parameter to be added to the beginning of FN's parameter list.  

   The other arguments are as for type_unification.  */

int
fn_type_unification (fn, explicit_targs, targs, args, return_type,
		     strict, extra_fn_arg)
     tree fn, explicit_targs, targs, args, return_type;
     unification_kind_t strict;
     tree extra_fn_arg;
{
  tree parms;

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

  parms = TYPE_ARG_TYPES (TREE_TYPE (fn));

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

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

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


/* 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 into which the deduced template
   parameter values are placed.  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.

   The EXPLICIT_TARGS are explicit template arguments provided via a
   template-id.

   The parameter STRICT is one of:

   DEDUCE_CALL: 
     We are deducing arguments for a function call, as in
     [temp.deduct.call].

   DEDUCE_CONV:
     We are deducing arguments for a conversion function, as in 
     [temp.deduct.conv].

   DEDUCE_EXACT:
     We are deducing arguments when calculating the partial
     ordering between specializations of function or class
     templates, as in [temp.func.order] and [temp.class.order],
     when doing an explicit instantiation as in [temp.explicit],
     when determining an explicit specialization as in
     [temp.expl.spec], or when taking the address of a function
     template, as in [temp.deduct.funcaddr].  */

int
type_unification (tparms, targs, parms, args, explicit_targs,
		  strict, allow_incomplete)
     tree tparms, targs, parms, args, explicit_targs;
     unification_kind_t strict;
     int allow_incomplete;
{
  int* explicit_mask;
  int i;

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

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

      if (arg_vec == error_mark_node)
	return 1;

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

  return 
    type_unification_real (tparms, targs, parms, args, 0,
			   strict, allow_incomplete, explicit_mask); 
}

/* Adjust types before performing type deduction, as described in
   [temp.deduct.call] and [temp.deduct.conv].  The rules in these two
   sections are symmetric.  PARM is the type of a function parameter
   or the return type of the conversion function.  ARG is the type of
   the argument passed to the call, or the type of the value
   intialized with the result of the conversion function.  */

void
maybe_adjust_types_for_deduction (strict, parm, arg)
     unification_kind_t strict;
     tree* parm;
     tree* arg;
{
  switch (strict)
    {
    case DEDUCE_CALL:
      break;

    case DEDUCE_CONV:
      {
	/* Swap PARM and ARG throughout the remainder of this
	   function; the handling is precisely symmetric since PARM
	   will initialize ARG rather than vice versa.  */
	tree* temp = parm;
	parm = arg;
	arg = temp;
	break;
      }

    case DEDUCE_EXACT:
      /* There is nothing to do in this case.  */
      return;

    default:
      my_friendly_abort (0);
    }

  if (TREE_CODE (*parm) != REFERENCE_TYPE)
    {
      /* [temp.deduct.call]
	 
	 If P is not a reference type:
	 
	 --If A is an array type, the pointer type produced by the
	 array-to-pointer standard conversion (_conv.array_) is
	 used in place of A for type deduction; otherwise,
	 
	 --If A is a function type, the pointer type produced by
	 the function-to-pointer standard conversion
	 (_conv.func_) is used in place of A for type deduction;
	 otherwise,
	 
	 --If A is a cv-qualified type, the top level
	 cv-qualifiers of A's type are ignored for type
	 deduction.  */
      if (TREE_CODE (*arg) == ARRAY_TYPE)
	*arg = build_pointer_type (TREE_TYPE (*arg));
      else if (TREE_CODE (*arg) == FUNCTION_TYPE
	  || TREE_CODE (*arg) == METHOD_TYPE)
	*arg = build_pointer_type (*arg);
      else
	*arg = TYPE_MAIN_VARIANT (*arg);
    }
  
  /* [temp.deduct.call]
     
     If P is a cv-qualified type, the top level cv-qualifiers
     of P's type are ignored for type deduction.  If P is a
     reference type, the type referred to by P is used for
     type deduction.  */
  *parm = TYPE_MAIN_VARIANT (*parm);
  if (TREE_CODE (*parm) == REFERENCE_TYPE)
    *parm = TREE_TYPE (*parm);
}

/* Like type_unfication.  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.  

   If SUBR is 1, we're being called recursively (to unify the
   arguments of a function or method parameter of a function
   template).  */

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

  my_friendly_assert (TREE_CODE (tparms) == TREE_VEC, 289);
  my_friendly_assert (parms == NULL_TREE 
		      || TREE_CODE (parms) == TREE_LIST, 290);
  /* ARGS could be NULL (via a call from parse.y to
     build_x_function_call).  */
  if (args)
    my_friendly_assert (TREE_CODE (args) == TREE_LIST, 291);
  my_friendly_assert (ntparms > 0, 292);

  switch (strict)
    {
    case DEDUCE_CALL:
      sub_strict = UNIFY_ALLOW_MORE_CV_QUAL | UNIFY_ALLOW_DERIVED;
      break;
      
    case DEDUCE_CONV:
      sub_strict = UNIFY_ALLOW_LESS_CV_QUAL;
      break;

    case DEDUCE_EXACT:
      sub_strict = UNIFY_ALLOW_NONE;
      break;
      
    default:
      my_friendly_abort (0);
    }

  while (parms
	 && parms != void_list_node
	 && args
	 && args != void_list_node)
    {
      parm = TREE_VALUE (parms);
      parms = TREE_CHAIN (parms);
      arg = TREE_VALUE (args);
      args = TREE_CHAIN (args);

      if (arg == error_mark_node)
	return 1;
      if (arg == unknown_type_node)
	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 == DEDUCE_EXACT)
	    {
	      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) == OVERLOAD
	      && TREE_CODE (OVL_FUNCTION (arg)) == TEMPLATE_DECL)
	    {
	      tree targs;
	      tree arg_type;

	      /* Have to back unify here */
	      arg = OVL_FUNCTION (arg);
	      targs = make_scratch_vec (DECL_NTPARMS (arg));
	      arg_type = TREE_TYPE (arg);
	      maybe_adjust_types_for_deduction (strict, &parm, &arg_type);
	      parm = expr_tree_cons (NULL_TREE, parm, NULL_TREE);
	      arg_type = scratch_tree_cons (NULL_TREE, arg_type, NULL_TREE);
	      return 
		type_unification (DECL_INNERMOST_TEMPLATE_PARMS (arg), 
				  targs, arg_type, parm, NULL_TREE,
				  DEDUCE_EXACT, 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)
	maybe_adjust_types_for_deduction (strict, &parm, &arg);

      switch (unify (tparms, targs, parm, arg, sub_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;
    }
}

/* Decide whether ARG can be unified with PARM, considering only the
   cv-qualifiers of each type, given STRICT as documented for unify.
   Returns non-zero iff the unification is OK on that basis.*/

int
check_cv_quals_for_unify (strict, arg, parm)
     int strict;
     tree arg;
     tree parm;
{
  return !((!(strict & UNIFY_ALLOW_MORE_CV_QUAL)
	    && (TYPE_READONLY (arg) < TYPE_READONLY (parm)
		|| TYPE_VOLATILE (arg) < TYPE_VOLATILE (parm)))
	   || (!(strict & UNIFY_ALLOW_LESS_CV_QUAL)
	       && (TYPE_READONLY (arg) > TYPE_READONLY (parm)
		   || TYPE_VOLATILE (arg) > TYPE_VOLATILE (parm))));
}

/* Takes parameters as for type_unification.  Returns 0 if the
   type deduction suceeds, 1 otherwise.  The parameter STRICT is a
   bitwise or of the following flags:

     UNIFY_ALLOW_NONE:
       Require an exact match between PARM and ARG.
     UNIFY_ALLOW_MORE_CV_QUAL:
       Allow the deduced ARG to be more cv-qualified than ARG.
     UNIFY_ALLOW_LESS_CV_QUAL:
       Allow the deduced ARG to be less cv-qualified than ARG.
     UNIFY_ALLOW_DERIVED:
       Allow the deduced ARG to be a template base class of ARG,
       or a pointer to a template base class of the type pointed to by
       ARG.  */

int
unify (tparms, targs, parm, arg, strict, explicit_mask)
     tree tparms, targs, parm, arg;
     int 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;

  /* Immediately reject some pairs that won't unify because of
     cv-qualification mismatches.  */
  if (TREE_CODE (arg) == TREE_CODE (parm)
      && TREE_CODE_CLASS (TREE_CODE (arg)) == 't'
      /* We check the cv-qualifiers when unifying with template type
	 parameters below.  We want to allow ARG `const T' to unify with
	 PARM `T' for example, when computing which of two templates
	 is more specialized, for example.  */
      && TREE_CODE (arg) != TEMPLATE_TYPE_PARM
      && !check_cv_quals_for_unify (strict, arg, parm))
    return 1;

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

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

      if (TEMPLATE_TYPE_LEVEL (parm)
	  != template_decl_level (tparm))
	/* The PARM is not one we're trying to unify.  Just check
	   to see if it matches ARG.  */
	return (TREE_CODE (arg) == TREE_CODE (parm)
		&& 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 Allocator = allocator> 
		   class vector.  */

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

		    /* This argument can be deduced.  */

		    if (unify (tparms, targs, t, 
			       TREE_VEC_ELT (argvec, i), 
			       UNIFY_ALLOW_NONE, explicit_mask))
		      return 1;
		  }
	      }
	      arg = CLASSTYPE_TI_TEMPLATE (arg);
	    }
	}
      else
	{
	  /* If PARM is `const T' and ARG is only `int', we don't have
	     a match unless we are allowing additional qualification.
	     If ARG is `const int' and PARM is just `T' that's OK;
	     that binds `const int' to `T'.  */
	  if (!check_cv_quals_for_unify (strict | UNIFY_ALLOW_LESS_CV_QUAL, 
					 arg, parm))
	    return 1;

	  /* Consider the case where ARG is `const volatile int' and
	     PARM is `const T'.  Then, T should be `volatile int'.  */
	  arg = 
	    cp_build_type_variant (arg, 
				   TYPE_READONLY (arg) > TYPE_READONLY (parm),
				   TYPE_VOLATILE (arg) > TYPE_VOLATILE (parm));
	}

      /* 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) ? 0 : 1;

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

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

      TREE_VEC_ELT (targs, idx) = copy_to_permanent (arg);
      return 0;

    case POINTER_TYPE:
      {
	int sub_strict;

	if (TREE_CODE (arg) == RECORD_TYPE && TYPE_PTRMEMFUNC_FLAG (arg))
	  return (unify (tparms, targs, parm, 
			 TYPE_PTRMEMFUNC_FN_TYPE (arg), strict,
			 explicit_mask)); 
	
	if (TREE_CODE (arg) != POINTER_TYPE)
	  return 1;
	
	/* [temp.deduct.call]

	   A can be another pointer or pointer to member type that can
	   be converted to the deduced A via a qualification
	   conversion (_conv.qual_).

	   We pass down STRICT here rather than UNIFY_ALLOW_NONE.
	   This will allow for additional cv-qualification of the
	   pointed-to types if appropriate.  In general, this is a bit
	   too generous; we are only supposed to allow qualification
	   conversions and this method will allow an ARG of char** and
	   a deduced ARG of const char**.  However, overload
	   resolution will subsequently invalidate the candidate, so
	   this is probably OK.  */
	sub_strict = strict;
	
	if (TREE_CODE (TREE_TYPE (arg)) != RECORD_TYPE
	    || TYPE_PTRMEMFUNC_FLAG (TREE_TYPE (arg)))
	  /* The derived-to-base conversion only persists through one
	     level of pointers.  */
	  sub_strict &= ~UNIFY_ALLOW_DERIVED;

	return unify (tparms, targs, TREE_TYPE (parm), TREE_TYPE
		      (arg), sub_strict,  explicit_mask);
      }

    case REFERENCE_TYPE:
      if (TREE_CODE (arg) != REFERENCE_TYPE)
	return 1;
      return unify (tparms, targs, TREE_TYPE (parm), TREE_TYPE (arg),
		    UNIFY_ALLOW_NONE, 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, TYPE_DOMAIN (parm),
		    TYPE_DOMAIN (arg), UNIFY_ALLOW_NONE, explicit_mask) != 0)
	return 1;
      return unify (tparms, targs, TREE_TYPE (parm), TREE_TYPE (arg),
		    UNIFY_ALLOW_NONE, 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, TYPE_MIN_VALUE (parm),
			TYPE_MIN_VALUE (arg), UNIFY_ALLOW_NONE, explicit_mask))
	    return 1;
	  if (TYPE_MAX_VALUE (parm) && TYPE_MAX_VALUE (arg)
	      && unify (tparms, targs, TYPE_MAX_VALUE (parm),
			TYPE_MAX_VALUE (arg), UNIFY_ALLOW_NONE, explicit_mask))
	    return 1;
	}
      else if (TREE_CODE (parm) == REAL_TYPE
	       /* We use the TYPE_MAIN_VARIANT since we have already
		  checked cv-qualification at the top of the
		  function.  */
	       && !comptypes (TYPE_MAIN_VARIANT (arg),
			      TYPE_MAIN_VARIANT (parm), 1))
	return 1;

      /* As far as unification is concerned, this wins.	 Later checks
	 will invalidate it if necessary.  */
      return 0;

      /* Types INTEGER_CST and MINUS_EXPR can come from array bounds.  */
      /* Type INTEGER_CST can come from ordinary constant template args.  */
    case INTEGER_CST:
      while (TREE_CODE (arg) == NOP_EXPR)
	arg = TREE_OPERAND (arg, 0);

      if (TREE_CODE (arg) != INTEGER_CST)
	return 1;
      return !tree_int_cst_equal (parm, arg);

    case TREE_VEC:
      {
	int i;
	if (TREE_CODE (arg) != TREE_VEC)
	  return 1;
	if (TREE_VEC_LENGTH (parm) != TREE_VEC_LENGTH (arg))
	  return 1;
	for (i = TREE_VEC_LENGTH (parm) - 1; i >= 0; i--)
	  if (unify (tparms, targs,
		     TREE_VEC_ELT (parm, i), TREE_VEC_ELT (arg, i),
		     UNIFY_ALLOW_NONE, explicit_mask))
	    return 1;
	return 0;
      }

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

      if (TREE_CODE (arg) != RECORD_TYPE)
	return 1;
  
      if (CLASSTYPE_TEMPLATE_INFO (parm) && uses_template_parms (parm))
	{
	  tree t = NULL_TREE;
	  if (strict & UNIFY_ALLOW_DERIVED)
	    /* [temp.deduct.call]

	       If P is a class, and P has the form template-id, then A
	       can be a derived class of the deduced A.  Likewise, if
	       P is a pointer to a class of the form template-id, A
	       can be a pointer to a derived class pointed to by the
	       deduced A.  */
	    t = get_template_base (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, CLASSTYPE_TI_ARGS (parm),
			CLASSTYPE_TI_ARGS (t), UNIFY_ALLOW_NONE,
			explicit_mask);
	}
      else if (!comptypes (TYPE_MAIN_VARIANT (parm),
			   TYPE_MAIN_VARIANT (arg), 1))
	return 1;
      return 0;

    case METHOD_TYPE:
    case FUNCTION_TYPE:
      if (TREE_CODE (arg) != TREE_CODE (parm))
	return 1;

      if (unify (tparms, targs, TREE_TYPE (parm),
		 TREE_TYPE (arg), UNIFY_ALLOW_NONE, explicit_mask))
	return 1;
      return type_unification_real (tparms, targs, TYPE_ARG_TYPES (parm),
				    TYPE_ARG_TYPES (arg), 1, 
				    DEDUCE_EXACT, 0, explicit_mask);

    case OFFSET_TYPE:
      if (TREE_CODE (arg) != OFFSET_TYPE)
	return 1;
      if (unify (tparms, targs, TYPE_OFFSET_BASETYPE (parm),
		 TYPE_OFFSET_BASETYPE (arg), UNIFY_ALLOW_NONE, explicit_mask))
	return 1;
      return unify (tparms, targs, TREE_TYPE (parm), TREE_TYPE (arg),
		    UNIFY_ALLOW_NONE, 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, t1, t, UNIFY_ALLOW_NONE,
			    explicit_mask);
	    }

	  if (!IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (tc)))
	    /* Good, we mangaged to simplify the exression.  */
	    return unify (tparms, targs, t, arg, UNIFY_ALLOW_NONE,
			  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;
    }
}

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 (TREE_PUBLIC (result))
	maybe_make_one_only (result);
    }
  else if (TREE_CODE (result) == FUNCTION_DECL)
    mark_inline_for_output (result);
}

/* Given two function templates PAT1 and PAT2, and explicit template
   arguments EXPLICIT_ARGS return:

   1 if PAT1 is more specialized than PAT2 as described in [temp.func.order].
   -1 if PAT2 is more specialized than PAT1.
   0 if neither is more specialized.  */
   
int
more_specialized (pat1, pat2, explicit_args)
     tree pat1, pat2, explicit_args;
{
  tree targs;
  int winner = 0;

  targs = get_bindings_overload (pat1, 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)),
			   DEDUCE_EXACT,
			   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, 
		     TREE_VEC_ELT (parms, i), TREE_VEC_ELT (args, i),
		     UNIFY_ALLOW_NONE, 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);
  }
}

/* Given a function DECL, which is a specialization of TEMP, modify
   DECL to be a re-instantiation of TEMPL with the same template
   arguments.

   One reason for doing this is a scenario like this:

     template <class T>
     void f(const T&, int i);

     void g() { f(3, 7); }

     template <class T>
     void f(const T& t, const int i) { }

   Note that when the template is first instantiated, with
   instantiate_template, the resulting DECL will have no name for the
   first parameter, and the wrong type for the second.  So, when we go
   to instantiate the DECL, we regenerate it.  */

void
regenerate_decl_from_template (decl, tmpl)
     tree decl;
     tree tmpl;
{
  tree args;
  tree save_ti;
  tree code_pattern;
  tree new_decl;

  args = DECL_TI_ARGS (decl);
  code_pattern = DECL_TEMPLATE_RESULT (tmpl);

  /* Trick tsubst into giving us a new decl.  CODE_PATTERN must be the
     most distant ancestor of DECL, since that's the one that will
     actually be altered by a redefinition.  */
  save_ti = DECL_TEMPLATE_INFO (code_pattern);
  DECL_TEMPLATE_INFO (code_pattern) = NULL_TREE;
  new_decl = tsubst (code_pattern, args, NULL_TREE);
  SET_DECL_IMPLICIT_INSTANTIATION (new_decl);
  DECL_TEMPLATE_INFO (code_pattern) = save_ti;

  if (TREE_CODE (decl) == VAR_DECL)
    {
      /* Set up DECL_INITIAL, since tsubst doesn't.  */
      pushclass (DECL_CONTEXT (decl), 2);
      DECL_INITIAL (new_decl) = 
	tsubst_expr (DECL_INITIAL (code_pattern), args, 
		     DECL_TI_TEMPLATE (decl));
      popclass (1);
    }

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

      if (DECL_TEMPLATE_SPECIALIZATION (new_decl) 
	  && !DECL_TEMPLATE_INFO (new_decl))
	/* Set up the information about what is being specialized. */
	DECL_TEMPLATE_INFO (new_decl) = DECL_TEMPLATE_INFO (decl);
    }

  duplicate_decls (new_decl, decl);

  if (TREE_CODE (decl) == FUNCTION_DECL)
    DECL_INITIAL (new_decl) = NULL_TREE;
}

/* 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;
  tree decl_pattern, code_pattern;
  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);

  if (pattern_defined)
    {
      repo_template_used (d);

      if (flag_external_templates && ! DECL_INTERFACE_KNOWN (d))
	{
	  if (flag_alt_external_templates)
	    {
	      if (interface_unknown)
		warn_if_unknown_interface (d);
	    }
	  else if (DECL_INTERFACE_KNOWN (code_pattern))
	    {
	      DECL_INTERFACE_KNOWN (d) = 1;
	      DECL_NOT_REALLY_EXTERN (d) = ! DECL_EXTERNAL (code_pattern);
	    }
	  else
	    warn_if_unknown_interface (code_pattern);
	}

      if (at_eof)
	import_export_decl (d);
    }

  /* Reject all external templates except inline functions.  */
  if (DECL_INTERFACE_KNOWN (d)
      && ! DECL_NOT_REALLY_EXTERN (d)
      && ! (TREE_CODE (d) == FUNCTION_DECL && DECL_INLINE (d)))
    goto out;

  if (TREE_CODE (d) == VAR_DECL 
      && TREE_READONLY (d)
      && DECL_INITIAL (d) == NULL_TREE
      && DECL_INITIAL (code_pattern) != NULL_TREE)
    /* We need to set up DECL_INITIAL regardless of pattern_defined if
	 the variable is a static const initialized in the class body.  */;
  else if (! pattern_defined
	   || (! (TREE_CODE (d) == FUNCTION_DECL && DECL_INLINE (d) && nested)
	       && ! at_eof))
    {
      /* Defer all templates except inline functions used in another
         function.  */
      lineno = line;
      input_filename = file;

      add_pending_template (d);
      goto out;
    }

  regenerate_decl_from_template (d, td);

  /* We already set the file and line above.  Reset them now in case
     they changed as a result of calling regenerate_decl_from_template.  */
  lineno = DECL_SOURCE_LINE (d);
  input_filename = DECL_SOURCE_FILE (d);

  if (TREE_CODE (d) == VAR_DECL)
    {
      DECL_IN_AGGR_P (d) = 0;
      if (DECL_INTERFACE_KNOWN (d))
	DECL_EXTERNAL (d) = ! DECL_NOT_REALLY_EXTERN (d);
      else
	{
	  DECL_EXTERNAL (d) = 1;
	  DECL_NOT_REALLY_EXTERN (d) = 1;
	}
      cp_finish_decl (d, DECL_INITIAL (d), NULL_TREE, 0, 0);
    }
  else if (TREE_CODE (d) == FUNCTION_DECL)
    {
      tree t = DECL_SAVED_TREE (code_pattern);

      start_function (NULL_TREE, d, NULL_TREE, 1);
      store_parm_decls ();

      if (t && TREE_CODE (t) == RETURN_INIT)
	{
	  store_return_init
	    (TREE_OPERAND (t, 0),
	     tsubst_expr (TREE_OPERAND (t, 1), args, 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;
}