https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101463
--- Comment #3 from GCC 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:5348e3cb9bc99d2ee4d7438b8eca5c92fff5b931 commit r15-3038-g5348e3cb9bc99d2ee4d7438b8eca5c92fff5b931 Author: Patrick Palka <ppa...@redhat.com> Date: Tue Aug 20 08:34:36 2024 -0400 c++: default targ eligibility refinement [PR101463] On Tue, 9 Jan 2024, Jason Merrill wrote: > On 1/5/24 15:01, Patrick Palka wrote[1]: > > Here during default template argument substitution we wrongly consider > > the (substituted) default arguments v and vt<int> as value-dependent[1] > > 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, which lets us accept both > > testcases by sidestepping the value_dependent_expression_p issue > > altogether. > > Hmm, maybe instead of substituting and asking if it's dependent, we should > specifically look for undeduced parameters. This patch implements this refinement, which incidentally fixes PR101463 just as well. [1]: https://gcc.gnu.org/pipermail/gcc-patches/2024-January/641957.html PR c++/101463 gcc/cp/ChangeLog: * pt.cc (type_unification_real): Directly look for undeduced parameters in the default argument instead of doing a trial substitution. gcc/testsuite/ChangeLog: * g++.dg/cpp1z/nontype6.C: New test. * g++.dg/cpp1z/nontype6a.C: New test. Reviewed-by: Jason Merrill <ja...@redhat.com>
