[Bug c++/115645] [12/13/14 Regression] new S[1][1]() requires non-explicit default ctor since r11-3092

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115645

--- Comment #8 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:bbc9c0423ca754e8e6ff80e08948ff52986337a0

commit r15-2435-gbbc9c0423ca754e8e6ff80e08948ff52986337a0
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Jul 17 15:44:26 2024 -0400

    c++: array new with value-initialization, again [PR115645]

    Unfortunately, my r15-1946 fix broke the attached testcase; the
    constexpr evaluation reported an error about not being able to
    evaluate the code emitted by build_vec_init.  Jason figured out
    it's because we were wrongly setting try_const to false, where
    in fact it should have been true.  Value-initialization of scalars
    is constexpr, so we should check that alongside of
    type_has_constexpr_default_constructor.

            PR c++/115645

    gcc/cp/ChangeLog:

            * init.cc (build_vec_init): When initializing a scalar type, try to
            create a constant initializer.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/constexpr-new23.C: New test.