[Bug c++/96330] Constexpr variables cannot be used in the template context.

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96330

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:574e7601829733d7cae20b5dc7034b876cc76b30

commit r11-7541-g574e7601829733d7cae20b5dc7034b876cc76b30
Author: Patrick Palka <ppalka@redhat.com>
Date:   Sat Mar 6 00:07:43 2021 -0500

    c++: Fix tsubsting member variable template-id [PR96330]

    This makes tsubst_copy appropriately handle a variable template-id, which
    in turn fixes tsubsting a COMPONENT_REF whose member operand is known at
    parse time to be a variable template-id, as in the initialization of 'x'
    in the first testcase.  Previously, we rejected this testcase with the
    error "foo_t::bar<T> is not a function template", issued from
    lookup_template_fuction.

    We were already properly handling the analagous case where the object
    operand of the COMPONENT_REF is dependent (and so the member operand is
    a dependent template name), but there doesn't seems to be existing test
    coverage for this, hence the second testcase below.

    gcc/cp/ChangeLog:

            PR c++/96330
            * pt.c (tsubst_copy) <case TEMPLATE_ID_EXPR>: Rename local
            variable 'fn' to 'tmpl'.  Handle a variable template-id by
            calling lookup_template_variable.

    gcc/testsuite/ChangeLog:

            PR c++/96330
            * g++.dg/cpp1y/var-templ68.C: New test.
            * g++.dg/cpp1y/var-templ68a.C: New test.

    Co-authored-by: Jakub Jelinek <jakub@redhat.com>