https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100374
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-12 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:90655e30130f8f609911335902db3c8354a5e21a commit r12-8602-g90655e30130f8f609911335902db3c8354a5e21a Author: Patrick Palka <ppa...@redhat.com> Date: Fri Jun 3 09:29:12 2022 -0400 c++: don't substitute TEMPLATE_PARM_CONSTRAINTS [PR100374] This patch makes us avoid substituting into the TEMPLATE_PARM_CONSTRAINTS of each template parameter except as necessary for declaration matching, like we already do for the other constituent constraints of a declaration. This patch also improves the CA104 implementation of explicit specialization matching of a constrained function template inside a class template, by considering the function's combined constraints instead of just its trailing constraints. This allows us to correctly handle the first three explicit specializations in concepts-spec2.C below, but because we compare the constraints as a whole, it means we incorrectly accept the fourth explicit specialization which writes #3's constraints in a different way. For complete correctness here, determine_specialization should use tsubst_each_template_parm_constraints and template_parameter_heads_equivalent_p. PR c++/100374 gcc/cp/ChangeLog: * pt.cc (determine_specialization): Compare overall constraints not just the trailing constraints. (tsubst_each_template_parm_constraints): Define. (tsubst_friend_function): Use it. (tsubst_friend_class): Use it. (tsubst_template_parm): Don't substitute TEMPLATE_PARM_CONSTRAINTS. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-spec2.C: New test. * g++.dg/cpp2a/concepts-template-parm11.C: New test. (cherry picked from commit 43c013df02fdb07f9b7a5e7e6669e6d69769d451)
