https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100893
--- Comment #2 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:6f8c9691495ad5a307db98dc19c3296ee4e6de64 commit r12-1224-g6f8c9691495ad5a307db98dc19c3296ee4e6de64 Author: Patrick Palka <ppa...@redhat.com> Date: Fri Jun 4 14:08:26 2021 -0400 c++: top-level cv-quals on type of NTTP [PR100893] Here, we're rejecting the specialization of g<T,F> with T=A, F=&f in param4.C below due to a spurious constness mismatch between the type of the template argument &f and the substituted type of the parm F (the latter has a top-level const). Note that this mismatch doesn't occur with object pointers because in that case a call to perform_qualification_conversions from convert_nontype_argument implicitly adds a top-level const to the argument (via a cast) to match. This however seems to be a manifestation of a more general conformance issue: we're not dropping top-level cv-quals on the substituted type of an NTTP as per [temp.param]/6 (we only do so at parse time in process_template_parm). So this patch makes convert_template_argument drop top-level cv-quals accordingly. PR c++/100893 gcc/cp/ChangeLog: * pt.c (convert_template_argument): Strip top-level cv-quals on the substituted type of a non-type template parameter. gcc/testsuite/ChangeLog: * g++.dg/template/param4.C: New test. * g++.dg/template/param5.C: New test. * g++.dg/cpp1z/nontype-auto19.C: New test. * g++.dg/cpp2a/concepts-decltype.C: Don't expect that the deduced type of a decltype(auto) NTTP has top-level cv-quals.
