DR 2179

	DR 2179
	* pt.c (process_partial_specialization): Handle error_mark_node
	from most_specialized_partial_spec.

From-SVN: r229395

gcc/cp/ChangeLog

+2015-10-25  Jason Merrill  <jason@redhat.com>
+
+	DR 2179
+	* pt.c (process_partial_specialization): Handle error_mark_node
+	from most_specialized_partial_spec.
+
 2015-10-23  Jason Merrill  <jason@redhat.com>
 
 	DR 1518

gcc/cp/pt.c

@@ -4690,14 +4690,18 @@ process_partial_specialization (tree decl)
 	  : DECL_TEMPLATE_INSTANTIATION (instance))
 	{
 	  tree spec = most_specialized_partial_spec (instance, tf_none);
-	  if (spec && TREE_VALUE (spec) == tmpl)
-	    {
-	      tree inst_decl = (DECL_P (instance)
-				? instance : TYPE_NAME (instance));
-	      permerror (input_location,
-			 "partial specialization of %qD after instantiation "
-			 "of %qD", decl, inst_decl);
-	    }
+	  tree inst_decl = (DECL_P (instance)
+			    ? instance : TYPE_NAME (instance));
+	  if (!spec)
+	    /* OK */;
+	  else if (spec == error_mark_node)
+	    permerror (input_location,
+		       "declaration of %qD ambiguates earlier template "
+		       "instantiation for %qD", decl, inst_decl);
+	  else if (TREE_VALUE (spec) == tmpl)
+	    permerror (input_location,
+		       "partial specialization of %qD after instantiation "
+		       "of %qD", decl, inst_decl);
 	}
     }
 

gcc/testsuite/g++.dg/template/partial-specialization3.C

+// DR 2179
+
+template <class T1, class T2> class A;
+template <class T> struct A<T, void> { void f(); };
+template <class T> void g(T) { A<char, void>().f(); }   // #1
+template<typename T> struct A<char, T> {};		// { dg-error "" }
+A<char, void> f;   // #2