[C++] PR 51989

Index: testsuite/g++.dg/cpp0x/sfinae32.C
===================================================================
--- testsuite/g++.dg/cpp0x/sfinae32.C	(revision 0)
+++ testsuite/g++.dg/cpp0x/sfinae32.C	(revision 0)
@@ -0,0 +1,18 @@ 
+// PR c++/51989
+// { dg-options -std=c++0x }
+
+template <typename T>
+struct is_container
+{
+  template <typename U, typename V = decltype(((U*)0)->begin())>
+  static char test(U* u);
+
+  template <typename U> static long test(...);
+
+  enum { value = sizeof test<T>(0) == 1 };
+};
+
+int main()
+{
+  return is_container<void>::value;
+}
Index: cp/typeck2.c
===================================================================
--- cp/typeck2.c	(revision 183555)
+++ cp/typeck2.c	(working copy)
@@ -1462,7 +1462,7 @@  build_scoped_ref (tree datum, tree basetype, tree*
    delegation is detected.  */
 
 tree
-build_x_arrow (tree expr)
+build_x_arrow (tree expr, tsubst_flags_t complain)
 {
   tree orig_expr = expr;
   tree type = TREE_TYPE (expr);
@@ -1486,7 +1486,7 @@  tree
 
       while ((expr = build_new_op (COMPONENT_REF, LOOKUP_NORMAL, expr,
 				   NULL_TREE, NULL_TREE,
-				   &fn, tf_warning_or_error)))
+				   &fn, complain)))
 	{
 	  if (expr == error_mark_node)
 	    return error_mark_node;
@@ -1497,7 +1497,8 @@  tree
 
 	  if (vec_member (TREE_TYPE (expr), types_memoized))
 	    {
-	      error ("circular pointer delegation detected");
+	      if (complain & tf_error)
+		error ("circular pointer delegation detected");
 	      return error_mark_node;
 	    }
 
@@ -1510,7 +1511,8 @@  tree
 
       if (last_rval == NULL_TREE)
 	{
-	  error ("base operand of %<->%> has non-pointer type %qT", type);
+	  if (complain & tf_error)
+	    error ("base operand of %<->%> has non-pointer type %qT", type);
 	  return error_mark_node;
 	}
 
@@ -1530,13 +1532,16 @@  tree
 	  return expr;
 	}
 
-      return cp_build_indirect_ref (last_rval, RO_NULL, tf_warning_or_error);
+      return cp_build_indirect_ref (last_rval, RO_NULL, complain);
     }
 
-  if (types_memoized)
-    error ("result of %<operator->()%> yields non-pointer result");
-  else
-    error ("base operand of %<->%> is not a pointer");
+  if (complain & tf_error)
+    {
+      if (types_memoized)
+	error ("result of %<operator->()%> yields non-pointer result");
+      else
+	error ("base operand of %<->%> is not a pointer");
+    }
   return error_mark_node;
 }
 
Index: cp/pt.c
===================================================================
--- cp/pt.c	(revision 183555)
+++ cp/pt.c	(working copy)
@@ -13678,7 +13678,7 @@  tsubst_copy_and_build (tree t,
       /* Remember that there was a reference to this entity.  */
       if (DECL_P (op1))
 	mark_used (op1);
-      return build_x_arrow (op1);
+      return build_x_arrow (op1, complain);
 
     case NEW_EXPR:
       {
Index: cp/parser.c
===================================================================
--- cp/parser.c	(revision 183555)
+++ cp/parser.c	(working copy)
@@ -5910,7 +5910,8 @@  cp_parser_postfix_dot_deref_expression (cp_parser
 
   /* If this is a `->' operator, dereference the pointer.  */
   if (token_type == CPP_DEREF)
-    postfix_expression = build_x_arrow (postfix_expression);
+    postfix_expression = build_x_arrow (postfix_expression,
+					tf_warning_or_error);
   /* Check to see whether or not the expression is type-dependent.  */
   dependent_p = type_dependent_expression_p (postfix_expression);
   /* The identifier following the `->' or `.' is not qualified.  */
Index: cp/cp-tree.h
===================================================================
--- cp/cp-tree.h	(revision 183555)
+++ cp/cp-tree.h	(working copy)
@@ -5876,7 +5876,7 @@  extern void check_narrowing			(tree, tree);
 extern tree digest_init				(tree, tree, tsubst_flags_t);
 extern tree digest_init_flags			(tree, tree, int);
 extern tree build_scoped_ref			(tree, tree, tree *);
-extern tree build_x_arrow			(tree);
+extern tree build_x_arrow			(tree, tsubst_flags_t);
 extern tree build_m_component_ref		(tree, tree);
 extern tree build_functional_cast		(tree, tree, tsubst_flags_t);
 extern tree add_exception_specifier		(tree, tree, int);