===================================================================
@@ -12252,6 +12252,12 @@ cp_parser_decltype_expr (cp_parser *parser,
/*declarator_p=*/false,
/*optional_p=*/false);
+ /* The production ~ class-name is not ok here, keep looking, it's probably
+ a complement expression (c++/65091). */
+ if (TREE_CODE (expr) == BIT_NOT_EXPR
+ && identifier_p (TREE_OPERAND (expr, 0)))
+ expr = error_mark_node;
+
if (!cp_parser_error_occurred (parser) && expr != error_mark_node)
{
bool non_integral_constant_expression_p = false;
===================================================================
@@ -0,0 +1,9 @@
+// PR c++/65091
+// { dg-do compile { target c++11 } }
+
+template<typename T>
+auto foo(T x) -> decltype(~x)
+{ return ~x; }
+
+int bar()
+{ return foo(10); }
Hi, I have been looking into this issue, which should be rather easy to solve: the problem seems that in a template we are mishandling ~ as a bitwise complement operator (vs destructor introducer). We end up here in cp_parser_unqualified_id: type_decl = cp_parser_class_name (parser, /*typename_keyword_p=*/false, /*template_keyword_p=*/false, typename_type, /*check_dependency=*/false, /*class_head_p=*/false, declarator_p); if (processing_template_decl && ! cp_parser_parse_definitely (parser)) { /* We couldn't find a type with this name, so just accept it and check for a match at instantiation time. */ type_decl = cp_parser_identifier (parser); if (type_decl != error_mark_node) type_decl = build_nt (BIT_NOT_EXPR, type_decl); return type_decl; } and apparently the cp_parser_id_expression call at the beginning of cp_parser_decltype_expr succeeds with a BIT_NOT_EXPR with an identifier as argument. But that means that we are looking into the ~ class-name production, which obviously doesn't make sense as decltype expression. If we keep on working in cp_parser_decltype_expr we end up calling cp_parser_expression (the same we do for things like !x or ++x) and everything goes well. Anyway, draft tested on x86_64-linux. Thanks! Paolo. //////////////////////////////