[Bug c++/101247] ICE when using static constexpr bool defined in parent-class in nested class constructor requires-clause

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

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
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:6d11dd94e53103641f9826b14e3086399f2a948c

commit r11-8733-g6d11dd94e53103641f9826b14e3086399f2a948c
Author: Patrick Palka <ppalka@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)