PR c++/71569 - decltype of template.

	* parser.c (cp_parser_decltype_expr): Handle missing template args.

From-SVN: r258110

gcc/cp/ChangeLog

+2018-03-01  Jason Merrill  <jason@redhat.com>
+
+	PR c++/71569 - decltype of template.
+	* parser.c (cp_parser_decltype_expr): Handle missing template args.
+
 2018-03-01  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/84596

gcc/cp/parser.c

@@ -13983,6 +13983,10 @@ cp_parser_decltype_expr (cp_parser *parser,
 	expr = cp_parser_lookup_name_simple (parser, expr,
 					     id_expr_start_token->location);
 
+      if (expr && TREE_CODE (expr) == TEMPLATE_DECL)
+	/* A template without args is not a complete id-expression.  */
+	expr = error_mark_node;
+
       if (expr
           && expr != error_mark_node
           && TREE_CODE (expr) != TYPE_DECL
@@ -14048,6 +14052,9 @@ cp_parser_decltype_expr (cp_parser *parser,
          expression.  */
       cp_parser_abort_tentative_parse (parser);
 
+      /* Commit to the tentative_firewall so we get syntax errors.  */
+      cp_parser_commit_to_tentative_parse (parser);
+
       /* Parse a full expression.  */
       expr = cp_parser_expression (parser, /*pidk=*/NULL, /*cast_p=*/false,
 				   /*decltype_p=*/true);

gcc/testsuite/g++.dg/cpp0x/decltype-33837.C

@@ -2,6 +2,6 @@
 // PR c++/33837
 void foo()
 {
-  __decltype (A::foo()); // { dg-error "was not declared|expected" }
-  __decltype (B); // { dg-error "was not declared" }
+  __decltype (A::foo()); // { dg-error "A" }
+  __decltype (B); // { dg-error "B" }
 }

gcc/testsuite/g++.dg/cpp0x/decltype43.C

@@ -22,6 +22,6 @@ struct B
 int main()
 {
   int x = B<decltype(A<int>::a(1))>::b(A<int>::a(1));
-  int y = B<decltype(A     ::a(2))>::b(A<int>::a(2)); // { dg-error "template argument" }
+  int y = B<decltype(A     ::a(2))>::b(A<int>::a(2)); // { dg-error "template" }
   return x + y;
 }

gcc/testsuite/g++.dg/cpp1y/var-templ59.C

+// PR c++/71569
+// { dg-do compile { target c++14 } }
+
+template <class T>
+struct A {
+  template <class U>
+  static U u;
+};
+
+int main()
+{
+  decltype(A<int>::u) a;	// { dg-error "missing template arguments" }
+  return a;
+}