[patch] Fix PR c++/25854: Bogus diagnostic with '<type error>'

[Volker Reichelt]

For the testcase

  template<typename> struct A {};
  template<> struct A<> {};

we issue the following diagnostic:

  diag.cc:2: error: wrong number of template arguments (0, should be 1)
  diag.cc:1: error: provided for 'template<class> struct A'
  diag.cc:2: error: explicit specialization of non-template '<type error>'

The third line (which wasn't emitted before GCC 3.4.0) is clearly bogus.
This happens because we pass an error_mark_node as argument to
maybe_process_partial_specialization, which cannot do anything
useful with this input and gives this bogus diagnostic.

The fix is to return early on such input.

Bootstrapped and regtested on x86_64-unknown-linux-gnu.
Ok for mainline, 4.1 branch, 4.0 branch, and 3.4 branch?

Regards,
Volker


:ADDPATCH C++:


2006-01-19  Volker Reichelt  <reichelt@igpm.rwth-aachen.de>

	PR c++/25854
	* pt.c (maybe_process_partial_specialization): Return early on
	error_mark_node.

====================================================================
--- gcc/gcc/cp/pt.c	2006-01-07 21:26:41 +0100
+++ gcc/gcc/cp/pt.c	2006-01-07 21:24:52 +0100
@@ -678,8 +678,12 @@ check_explicit_instantiation_namespace (
 void
 maybe_process_partial_specialization (tree type)
 {
-  /* TYPE maybe an ERROR_MARK_NODE.  */
-  tree context = TYPE_P (type) ? TYPE_CONTEXT (type) : NULL_TREE;
+  tree context;
+
+  if (type == error_mark_node)
+    return;
+
+  context = TYPE_CONTEXT (type);
 
   if (CLASS_TYPE_P (type) && CLASSTYPE_USE_TEMPLATE (type))
     {
====================================================================

2006-01-19  Volker Reichelt  <reichelt@igpm.rwth-aachen.de>

	PR c++/25854
	* g++.dg/template/spec28.C: New test.

====================================================================
--- gcc/gcc/testsuite/g++.dg/template/spec28.C   2005-08-29 00:25:44 +0200
+++ gcc/gcc/testsuite/g++.dg/template/spec28.C   2006-01-09 18:48:42 +0100
@@ -0,0 +1,6 @@
+// PR c++/25854
+// Bad diagnostic
+// { dg-do compile }
+
+template<typename> struct A {};  // { dg-error "provided" }
+template<> struct A<> {};        // { dg-error "wrong number" }
====================================================================