PR c++/71193 - incomplete types in templates

	* parser.c (cp_parser_postfix_dot_deref_expression): In a template
	handle incomplete type by pedwarning and then treating as dependent.

From-SVN: r245223

gcc/cp/ChangeLog

+2017-02-06  Jason Merrill  <jason@redhat.com>
+
+	PR c++/71193 - incomplete types in templates
+	* parser.c (cp_parser_postfix_dot_deref_expression): In a template
+	handle incomplete type by pedwarning and then treating as dependent.
+
 2017-02-06  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/79379

gcc/cp/parser.c

@@ -7309,7 +7309,7 @@ cp_parser_postfix_dot_deref_expression (cp_parser *parser,
 
   /* Enter the scope corresponding to the type of the object
      given by the POSTFIX_EXPRESSION.  */
-  if (!dependent_p && TREE_TYPE (postfix_expression) != NULL_TREE)
+  if (!dependent_p)
     {
       scope = TREE_TYPE (postfix_expression);
       /* According to the standard, no expression should ever have
@@ -7324,11 +7324,33 @@ cp_parser_postfix_dot_deref_expression (cp_parser *parser,
 	 required to be of complete type for purposes of class member
 	 access (5.2.5) outside the member function body.  */
       if (postfix_expression != current_class_ref
+	  && scope != error_mark_node
 	  && !(processing_template_decl
 	       && current_class_type
 	       && (same_type_ignoring_top_level_qualifiers_p
 		   (scope, current_class_type))))
-	scope = complete_type_or_else (scope, postfix_expression);
+	{
+	  scope = complete_type (scope);
+	  if (!COMPLETE_TYPE_P (scope))
+	    {
+	      /* In a template, be permissive by treating an object expression
+		 of incomplete type as dependent (after a pedwarn).  */
+	      diagnostic_t kind = (processing_template_decl
+				   ? DK_PEDWARN
+				   : DK_ERROR);
+	      cxx_incomplete_type_diagnostic
+		(location_of (postfix_expression),
+		 postfix_expression, scope, kind);
+	      if (processing_template_decl)
+		{
+		  dependent_p = true;
+		  scope = TREE_TYPE (postfix_expression) = NULL_TREE;
+		}
+	    }
+	}
+
+      if (!dependent_p)
+	{
 	  /* Let the name lookup machinery know that we are processing a
 	     class member access expression.  */
 	  parser->context->object_type = scope;
@@ -7343,7 +7365,9 @@ cp_parser_postfix_dot_deref_expression (cp_parser *parser,
 	  if (scope == error_mark_node)
 	    postfix_expression = error_mark_node;
 	}
-  else
+    }
+
+  if (dependent_p)
     /* Tell cp_parser_lookup_name that there was an object, even though it's
        type-dependent.  */
     parser->context->object_type = unknown_type_node;

gcc/testsuite/g++.dg/template/incomplete8.C

+// PR c++/71193
+// { dg-options "" }
+
+class Heap;
+class A {
+public:  
+  Heap *m_fn1();
+};
+template <typename> class B : A {
+  void m_fn2() { m_fn1()->HashSeed; } // { dg-warning "incomplete" }
+};