https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111485
--- Comment #4 from GCC 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:f24d6f0031fd515e6497c8c96446afd02aa4dbaa commit r12-10068-gf24d6f0031fd515e6497c8c96446afd02aa4dbaa Author: Patrick Palka <ppa...@redhat.com> Date: Fri Sep 22 06:25:49 2023 -0400 c++: constraint rewriting during ttp coercion [PR111485] In order to compare the constraints of a ttp with that of its argument, we rewrite the ttp's constraints in terms of the argument template's template parameters. The substitution to achieve this currently uses a single level of template arguments, but that never does the right thing because a ttp's template parameters always have level >= 2. This patch fixes this by including the outer template arguments in the substitution, which ought to match the depth of the ttp. The second testcase demonstrates it's better to substitute the concrete outer template arguments instead of generic ones since a ttp's constraints could depend on outer parameters. PR c++/111485 gcc/cp/ChangeLog: * pt.cc (is_compatible_template_arg): New parameter 'args'. Add the outer template arguments 'args' to 'new_args'. (convert_template_argument): Pass 'args' to is_compatible_template_arg. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-ttp5.C: New test. * g++.dg/cpp2a/concepts-ttp6.C: New test. (cherry picked from commit 6f902a42b0afe3f3145bcb864695fc290b5acc3e)
