[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

--- Comment #13 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:c3afdb8ba8f1839544c414f57e41a58c8fda5349

commit r14-708-gc3afdb8ba8f1839544c414f57e41a58c8fda5349
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu May 11 10:04:25 2023 -0400

    c++: converted lambda as template argument [PR83258, ...]

    r8-1253-g3d2e25a240c711 removed the template argument linkage requirement
    in convert_nontype_argument for C++17 (which r9-3836-g4be5c72cf3ea3e later
    factored out into invalid_tparm_referent_p), but we need to also remove
    the one in convert_nontype_argument_function for benefit of the first and
    third testcase which we currently reject even in C++17/20 mode.

    And in invalid_tparm_referent_p we're inadvertendly returning false for
    the address of a lambda's static op() since it's DECL_ARTIFICIAL, which
    currently causes us to reject the second (C++20) testcase.  But this
    DECL_ARTIFICIAL check seems to be relevant only for VAR_DECL, and in fact
    this code path was originally reachable only for VAR_DECL until recently
    (r13-6970-gb5e38b1c166357).  So this patch restricts the check to VAR_DECL.

    Co-authored-by: Jonathan Wakely <jwakely@redhat.com>

            PR c++/83258
            PR c++/80488
            PR c++/97700

    gcc/cp/ChangeLog:

            * pt.cc (convert_nontype_argument_function): Remove linkage
            requirement for C++17 and later.
            (invalid_tparm_referent_p) <case ADDR_EXPR>: Restrict
            DECL_ARTIFICIAL rejection test to VAR_DECL.

    gcc/testsuite/ChangeLog:

            * g++.dg/ext/visibility/anon8.C: Don't expect a "no linkage"
            error for the template argument &B2:fn in C++17 mode.
            * g++.dg/cpp0x/lambda/lambda-conv15.C: New test.
            * g++.dg/cpp2a/nontype-class56.C: New test.
            * g++.dg/template/function2.C: New test.