https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103401
--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I think the patch might be just:
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -7508,6 +7508,8 @@ cp_parser_postfix_expression (cp_parser *parser, bool
address_p, bool cast_p,
looking at a functional cast. We could also be looking at
an id-expression. So, we try the functional cast, and if
that doesn't work we fall back to the primary-expression. */
+ auto cleanup = make_temp_override
+ (parser->auto_is_implicit_function_template_parm_p, false);
cp_parser_parse_tentatively (parser);
/* Look for the simple-type-specifier. */
++parser->prevent_constrained_type_specifiers;
Until C++23 auto(x), we didn't have to think about auto in a
parameter-decl-clause all that much I suspect.
