https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107437
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:982629bea416df976686467f235e09cb1a5531cc commit r13-4761-g982629bea416df976686467f235e09cb1a5531cc Author: Patrick Palka <ppa...@redhat.com> Date: Sat Dec 17 11:24:44 2022 -0500 c++: constantness of non-dependent NTTP argument [PR107437] Here we're rejecting the use of the lambda capture of 't' (of empty type) as a template argument ultimately because convert_nontype_argument checks constantness using is_constant_expression, which returns false for lambda captures since want_rval=false. But in this case I believe an lvalue-to-rvalue conversion of the argument is implied, so we should be using is_rvalue_constant_expression instead (which would return true here). However, it doesn't seem necessary to consider constantness at all when deciding whether to instantiate a non-dependent argument in convert_nontype_argument. So this patch gets rid of the problematic constantness test altogether, which incidentally also fixes the similar dg-ice'd testcase from PR87765. This is in line with a similar change we made to finish_decltype_type in r12-7564-gec0f53a3a542e7. PR c++/107437 PR c++/87765 gcc/cp/ChangeLog: * pt.cc (convert_nontype_argument): Relax is_nondep_const_expr test to !inst_dep_expr_p. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/lambda-generic-107437.C: New test. * g++.dg/cpp1z/constexpr-lambda26.C: Remove dg-ice.
