[Bug c++/105064] [10/11 Regression] requires crashes gcc

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105064

--- Comment #13 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:214330a15cd7fd52e574023152f1321c6d329e82

commit r11-9796-g214330a15cd7fd52e574023152f1321c6d329e82
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon Mar 28 14:15:16 2022 -0400

    c++: constrained template friend matching ICE [PR105064]

    Here during declaration matching for the two constrained template
    friends, we crash from maybe_substitute_reqs_for because the second
    friend doesn't yet have DECL_TEMPLATE_INFO set (we're being called
    indirectly from push_template_decl).

    As far as I can tell, this situation happens only when declaring a
    constrained template friend within a non-template class (as in the
    testcase), in which case the substitution would be a no-op anyway.
    So this patch rearranges maybe_substitute_reqs_for to gracefully
    handle missing DECL_TEMPLATE_INFO by just skipping the substitution.

            PR c++/105064

    gcc/cp/ChangeLog:

            * constraint.cc (maybe_substitute_reqs_for): Don't assume
            DECL_TEMPLATE_INFO is available.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/concepts-friend9.C: New test.

    (cherry picked from commit ecb4882e362e80a1bf172453ac9b366edbb4e89c)