[patch] Fix PR c++/28860: Trouble with bound template template parameter in specialization

[Volker Reichelt <reichelt at igpm dot rwth-aachen dot de>]

The compiler ICEs on the following invalid code snippet since GCC 3.0:

  template<template<int> class A> class A<0> {};

bug.cc:1: internal compiler error: tree check: expected record_type or union_type or qual_union_type, have bound_template_template_parm in xref_basetypes, at cp/decl.c:9788
Please submit a full bug report, [etc.]

In addition the compiler accepts the following similar invalid code snippet:

  template<template<int> class A> class A<0>;

The following patch adds a check for BOUND_TEMPLATE_TEMPLATE_PARM to
maybe_process_partial_specialization to emit a proper diagnostic in
both cases.

This wouldn't prevent the ICE in the first case, though. Therefore
the patch adds a return value to maybe_process_partial_specialization.
If an error occured the return value is an error_mark_node, otherwise
the TYPE is just passed through. In cp_parser_class_head the return
value is then used.

Bootstrapped and regtested on x86_64-unknown-linux-gnu.
Ok for mainline, 4.1 branch, and 4.0 branch?

Regards,
Volker

:ADDPATCH C++:


2006-08-26  Volker Reichelt  <reichelt@igpm.rwth-aachen.de>

	PR c++/28860
	* cp-tree.h (maybe_process_partial_specialization): Return
	tree instead of void.
	* parser.c (cp_parser_class_head): Use return value of
	maybe_process_partial_specialization.
	* pt.c (maybe_process_partial_specialization): Return error_mark_node
	for broken specializations, TYPE otherwise.  Check for template
	template parameters.

===================================================================
--- gcc/gcc/cp/cp-tree.h	2006-07-28 03:56:58 +0200
+++ gcc/gcc/cp/cp-tree.h	2006-08-20 02:38:17 +0200
@@ -4111,7 +4111,7 @@ extern int template_class_depth			(tree)
 extern int is_specialization_of			(tree, tree);
 extern bool is_specialization_of_friend		(tree, tree);
 extern int comp_template_args			(tree, tree);
-extern void maybe_process_partial_specialization (tree);
+extern tree maybe_process_partial_specialization (tree);
 extern tree most_specialized_instantiation	(tree);
 extern void print_candidates			(tree);
 extern void instantiate_pending_templates	(int);
===================================================================
--- gcc/gcc/cp/parser.c	2006-08-03 04:49:07 +0200
+++ gcc/gcc/cp/parser.c	2006-08-20 02:38:56 +0200
@@ -13329,7 +13329,7 @@ cp_parser_class_head (cp_parser* parser,
   if (template_id_p)
     {
       type = TREE_TYPE (id);
-      maybe_process_partial_specialization (type);
+      type = maybe_process_partial_specialization (type);
       if (nested_name_specifier)
 	pushed_scope = push_scope (nested_name_specifier);
     }
===================================================================
--- gcc/gcc/cp/pt.c	2006-08-09 20:43:06 +0200
+++ gcc/gcc/cp/pt.c	2006-08-20 02:37:38 +0200
@@ -674,13 +674,20 @@ check_explicit_instantiation_namespace (
 /* The TYPE is being declared.  If it is a template type, that means it
    is a partial specialization.  Do appropriate error-checking.  */
 
-void
+tree
 maybe_process_partial_specialization (tree type)
 {
   tree context;
 
   if (type == error_mark_node)
-    return;
+    return error_mark_node;
+
+  if (TREE_CODE (type) == BOUND_TEMPLATE_TEMPLATE_PARM)
+    {
+      error ("name of class shadows template template parameter %qD",
+	     TYPE_NAME (type));
+      return error_mark_node;
+    }
 
   context = TYPE_CONTEXT (type);
 
@@ -765,7 +772,12 @@ maybe_process_partial_specialization (tr
 	}
     }
   else if (processing_specialization)
-    error ("explicit specialization of non-template %qT", type);
+    {
+      error ("explicit specialization of non-template %qT", type);
+      return error_mark_node;
+    }
+
+  return type;
 }
 
 /* Returns nonzero if we can optimize the retrieval of specializations
===================================================================

2006-08-26  Volker Reichelt  <reichelt@igpm.rwth-aachen.de>

	PR c++/28860
	* g++.dg/template/ttp22.C: New test.

===================================================================
--- gcc/gcc/testsuite/g++.dg/template/ttp22.C	2003-09-23 19:59:22 +0200
+++ gcc/gcc/testsuite/g++.dg/template/ttp22.C	2006-08-20 00:52:06 +0200
@@ -0,0 +1,8 @@
+// PR c++/28860
+// { dg-do compile}
+
+template<template<int> class A>
+class A<0>;  // { dg-error "shadows template template parameter" }
+
+template<template<int> class B>
+class B<0> {};  // { dg-error "shadows template template parameter" }
===================================================================