https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101463
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-14 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:124f2f62e01c6f110279608ad09e0f1d378e4899 commit r14-10890-g124f2f62e01c6f110279608ad09e0f1d378e4899 Author: Patrick Palka <ppa...@redhat.com> Date: Tue Nov 5 15:18:26 2024 -0500 c++: reference variable as default targ [PR101463] Here during default template argument substitution we wrongly consider the (substituted) default arguments v and vt<int> as value-dependent which ultimately leads to deduction failure for the calls. The bogus value_dependent_expression_p result aside, I noticed type_unification_real during default targ substitution keeps track of whether all previous targs are known and non-dependent, as is the case for these calls. And in such cases it should be safe to avoid checking dependence of the substituted default targ and just assume it's not. This patch implements this optimization for GCC 14, which lets us accept both testcases by sidestepping the value_dependent_expression_p issue altogether. (Note that for GCC 15 we fixed this differently, see r15-3038-g5348e3cb9bc99d.) PR c++/101463 gcc/cp/ChangeLog: * pt.cc (type_unification_real): Avoid checking dependence of a substituted default template argument if we can assume it's non-dependent. gcc/testsuite/ChangeLog: * g++.dg/cpp1z/nontype6.C: New test. * g++.dg/cpp1z/nontype6a.C: New test. Reviewed-by: Jason Merrill <ja...@redhat.com>
