[Bug c++/80351] Inconsistent warning for constexpr auto constant when using initializer list (-Wunused-variable)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80351

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:8d0fcf135857869f7cff36d29bc3527c482372a9

commit r13-50-g8d0fcf135857869f7cff36d29bc3527c482372a9
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Mar 23 18:01:20 2022 -0700

    c++: check completeness after auto deduction [PR80351]

    Normally we check for incomplete type in start_decl, but that obviously
    doesn't work for auto variables. Thanks to Pokechu22 for the analysis and
    testcases:

    "When cp_finish_decl calls cp_apply_type_quals_to_decl on a const auto or
    constexpr auto variable, the type might not be complete the first time
    (this happened when auto deduces to an initializer_list).
    cp_apply_type_quals_to_decl removes the const qualifier if the type is
    not complete, which is appropriate for grokdeclarator, on the assumption
    that the type will be complete when called by cp_finish_decl."

            PR c++/80351

    gcc/cp/ChangeLog:

            * decl.cc (cp_finish_decl): Check completeness of deduced type.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp0x/constexpr-77482.C: Adjust message.
            * g++.dg/cpp1y/auto-fn27.C: Likewise.
            * g++.dg/cpp1y/lambda-generic-variadic22.C: Likewise.
            * g++.dg/cpp1z/decomp54.C: Likewise.
            * g++.dg/cpp0x/initlist-const1.C: New test.
            * g++.dg/warn/Wunused-var-37.C: New test.
            * g++.dg/warn/Wunused-var-38.C: New test.
            * g++.dg/warn/Wunused-var-39.C: New test.