pt.c (instantiate_class_template): Don't try to figure out what specialization…

pt.c (instantiate_class_template): Don't try to figure out what specialization to use for a partial instantiation.

	* pt.c (instantiate_class_template): Don't try to figure out what
	specialization to use for a partial instantiation.  Correct
	typos in a couple of comments.  Avoid calling uses_template_parms
	multiple times.

From-SVN: r23808

gcc/cp/ChangeLog

+1998-11-23  Mark Mitchell  <mark@markmitchell.com>
+
+	* pt.c (instantiate_class_template): Don't try to figure out what
+	specialization to use for a partial instantiation.  Correct
+	typos in a couple of comments.  Avoid calling uses_template_parms
+	multiple times.
+
 1998-11-23  Benjamin Kosnik  <bkoz@cygnus.com>
 
         * method.c (process_overload_item): Add call to

gcc/cp/pt.c

@@ -4452,6 +4452,7 @@ instantiate_class_template (type)
 {
   tree template, args, pattern, t;
   tree typedecl;
+  int is_partial_instantiation;
 
   if (type == error_mark_node)
     return error_mark_node;
@@ -4465,16 +4466,37 @@ instantiate_class_template (type)
      argument coercion and such is simply lost.  */
   push_momentary ();
 
+  /* Figure out which template is being instantiated.  */
   template = most_general_template (CLASSTYPE_TI_TEMPLATE (type));
-  args = CLASSTYPE_TI_ARGS (type);
   my_friendly_assert (TREE_CODE (template) == TEMPLATE_DECL, 279);
+
+  /* Figure out which arguments are being used to do the
+     instantiation.  */
+  args = CLASSTYPE_TI_ARGS (type);
+  is_partial_instantiation = uses_template_parms (args);
+
+  if (is_partial_instantiation)
+    /* There's no telling which specialization is appropriate at this
+       point.  Since all peeking at the innards of this partial
+       instantiation are extensions (like the "implicit typename"
+       extension, which allows users to omit the keyword `typename' on
+       names that are declared as types in template base classes), we
+       are free to do what we please.
+
+       Trying to figure out which partial instantiation to use can
+       cause a crash.  (Some of the template arguments don't even have
+       types.)  So, we just use the most general version.  */
+    t = NULL_TREE;
+  else
+    {
       t = most_specialized_class (template, args);
 
       if (t == error_mark_node)
 	{
 	  char *str = "candidates are:";
 	  cp_error ("ambiguous class template instantiation for `%#T'", type);
-      for (t = DECL_TEMPLATE_SPECIALIZATIONS (template); t; t = TREE_CHAIN (t))
+	  for (t = DECL_TEMPLATE_SPECIALIZATIONS (template); t; 
+	       t = TREE_CHAIN (t))
 	    {
 	      if (get_class_bindings (TREE_VALUE (t), TREE_PURPOSE (t),
 				      args))
@@ -4487,7 +4509,9 @@ instantiate_class_template (type)
 	  type = error_mark_node;
 	  goto end;
 	}
-  else if (t)
+    }
+
+  if (t)
     pattern = TREE_TYPE (t);
   else
     pattern = TREE_TYPE (template);
@@ -4523,14 +4547,14 @@ instantiate_class_template (type)
 	args = inner_args;
     }
 
-  if (pedantic && uses_template_parms (args))
+  if (pedantic && is_partial_instantiation)
     {
-      /* 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.  We do the
-	 type as complete so that, for example, declaring one of its
-	 members to be a friend will not be rejected.  */
+      /* If this is a partial instantiation, then we can't instantiate
+	 the type; there's no telling whether or not one of the
+	 template parameters might eventually be instantiated to some
+	 value that results in a specialization being used.  We do
+	 mark the type as complete so that, for example, declaring one
+	 of its members to be a friend will not be rejected.  */
       TYPE_SIZE (type) = integer_zero_node;
       goto end;
     }
@@ -4603,7 +4627,7 @@ instantiate_class_template (type)
   /* 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))
+  if (is_partial_instantiation)
     {
       TYPE_BINFO_BASETYPES (type) = TYPE_BINFO_BASETYPES (pattern);
       TYPE_FIELDS (type) = TYPE_FIELDS (pattern);
@@ -7335,7 +7359,7 @@ unify (tparms, targs, parm, arg, strict, explicit_mask)
     return 0;
 
   /* If PARM uses template parameters, then we can't bail out here,
-     even in ARG == PARM, since we won't record unifications for the
+     even if ARG == PARM, since we won't record unifications for the
      template parameters.  We might need them if we're trying to
      figure out which of two things is more specialized.  */
   if (arg == parm && !uses_template_parms (parm))

gcc/testsuite/g++.old-deja/g++.pt/spec25.C

+// Build don't link:
+
+template <class T, int I>
+struct S {
+};
+
+template <int I>
+struct S <double, I> {
+};
+
+template <class T>
+void f ()
+{
+  S<double, T::x> s;
+}