https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94592
--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:d419e176d74162af6513be0b3bc1031726543993 commit r10-7836-gd419e176d74162af6513be0b3bc1031726543993 Author: Marek Polacek <pola...@redhat.com> Date: Fri Apr 17 15:47:15 2020 -0400 c++: Fix ICE with { } as template argument [PR94592] As an extension (there should be a CWG about this though), we support braced-init-list as a template argument, but convert_nontype_argument had trouble digesting them. We ICEd because of the double coercion we perform for template arguments: convert_nontype_argument called from finish_template_type got a { }, and since a class type was involved and we were in a template, convert_like created an IMPLICIT_CONV_EXPR. Then the second conversion of the same argument crashed in constexpr.c because the IMPLICIT_CONV_EXPR had gotten wrapped in a TARGET_EXPR. Another issue was that an IMPLICIT_CONV_EXPR leaked to constexpr.c when building an aggregate init. We should have instantiated the IMPLICIT_CONV_EXPR in the first call to convert_nontype_argument, but we didn't, because the call to is_nondependent_constant_expression returned false because it checks !BRACE_ENCLOSED_INITIALIZER_P. Then non_dep was false even though the expression didn't contain anything dependent and we didn't instantiate it in convert_nontype_argument. To fix this, check BRACE_ENCLOSED_INITIALIZER_P in cxx_eval_outermost_constant_expr rather than in is_nondependent_*. PR c++/94592 * constexpr.c (cxx_eval_outermost_constant_expr): Return when T is a BRACE_ENCLOSED_INITIALIZER_P. (is_nondependent_constant_expression): Don't check BRACE_ENCLOSED_INITIALIZER_P. (is_nondependent_static_init_expression): Likewise. * g++.dg/cpp2a/nontype-class34.C: New test. * g++.dg/cpp2a/nontype-class35.C: New test.