[GNATS 21382] assertion failed at: "templates.c", line 2355 in template_template_arg_matches_param

[jhsedg]

Customer bug ID

contains.cpp

Description

​Reduced boost test.
​
​template <typename a, typename b = a> b c(int);
​template auto d() -> decltype(c(0));
​template using e = typename a ::f;
​struct g {
​ template constexpr auto operator()(h &&) const;
​} i;
​template <template class> struct j;
​template <template <typename...> class h> j k;
​template <typename h, typename... l, typename = decltype(d()(d...))>
​void m();
​template <typename...> void m();
​template struct n {
​ template <typename... l> void operator()(l...) { m<h, l...>; }
​};
​template constexpr auto g::operator()(h &&) const {
​ return n{};
​}
​main() {
​ using o = int;
​ auto q = i([](auto p) -> decltype(k<e<decltype(p)>::nested>) {});
​ q(o{});
​}
​
​[ellen@lin1 ~]$ eccp --c++17 --gnu=80300 /tmp/reduced.C
​"/tmp/reduced.C", line 18: warning: return type "int" omitted in declaration of
​ function "main"
​ main() {
​ ^
​
​"/tmp/reduced.C", line 13: warning: expression has no effect
​ template <typename... l> void operator()(l...) { m<h, l...>; }
​ ^
​
​"/tmp/reduced.C", line 2: internal error: assertion failed at: "templates.c",
​ line 2355 in template_template_arg_matches_param
​
​ template auto d() -> decltype(c(0));
​ ^
​
​1 catastrophic error detected in the compilation of "/tmp/reduced.C".
​Compilation aborted.
​Aborted (core dumped)
​eccp: front end returned an exit status of 134
​-----> Context in template_template_arg_matches_param ( ):
​ param_template);
​ } /* if /
​ / In EXPENSIVE_CHECKING configurations we make sure the new checking
​ is a superset of the old. */
​ check_assertion(!do_old_style_check ||
​ (old_style_match ? match : TRUE));
​-----> Abbreviated stack trace:
​assertion_failed
​template_template_arg_matches_param
​substitute_template_argument
​copy_template_arg_list_with_substitution
​copy_template_arg_list_with_substitution_rebuilding_arg_operands
​make_operand_for_rescanned_identifier
​rescan_expr_with_substitution_internal
​make_rescan_operand_full
​make_rescan_operand
​scan_decltype_operator
​decltype_of_expr_with_substitution
​-----> assertion_failed crash signatures: 4e4f9bbf7133315204d807df655815d0 from 0e0c1606008702aaec7c6c97082a