https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101247
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-11 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:6d11dd94e53103641f9826b14e3086399f2a948c commit r11-8733-g6d11dd94e53103641f9826b14e3086399f2a948c Author: Patrick Palka <ppa...@redhat.com> Date: Fri Jul 9 10:20:22 2021 -0400 c++: find_template_parameters and TEMPLATE_DECLs [PR101247] r12-1989 fixed the testcase in the PR, but unfortunately the fix is buggy: it breaks the case where the common template between the TEMPLATE_DECL t and ctx_parms is the innermost template (as in concepts-memtmpl5.C below). This can be fixed by instead passing the TREE_TYPE of ctmpl to common_enclosing_class when ctmpl is a class template. But even after that's fixed, the analogous case where the innermost template is a partial specialization is still broken (as in concepts-memtmpl5a.C below), because ctmpl is always a primary template. So this patch instead takes a diferent approach that doesn't rely on ctx_parms at all: when looking for the template parameters of a TEMPLATE_DECL that are shared with the current template context, just walk its DECL_CONTEXT. As long as the template is not overly general (e.g. we didn't pass it through most_general_template), this should give us exactly what we want, since if a TEMPLATE_DECL can be referred to from some template context then the template parameters it uses must all be in-scope and contained in its DECL_CONTEXT. This effectively makes us treat TEMPLATE_DECLs more similarly to other _DECLs (whose DECL_CONTEXT we also walk). PR c++/101247 gcc/cp/ChangeLog: * pt.c (any_template_parm_r) <case TEMPLATE_DECL>: Just walk the DECL_CONTEXT. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-memtmpl4.C: Uncomment the commented out example, which we now handle correctly. * g++.dg/cpp2a/concepts-memtmpl5.C: New test. * g++.dg/cpp2a/concepts-memtmpl5a.C: New test. (cherry picked from commit f53e66019df819f55d424cc56f8b0ea81c074b55)
