[Bug c++/98810] [9/10 Regression] [C++20] ICE in tsubst_copy, at cp/pt.c:16771

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98810

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:bf49d83570ddb4df7893c3d605f7fc89db13792d

commit r10-9412-gbf49d83570ddb4df7893c3d605f7fc89db13792d
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Feb 25 16:47:53 2021 -0500

    c++: Fix class NTTP constness handling [PR98810]

    Here, when substituting still-dependent args into an alias template, we see
    a non-const type because the default argument is non-const, and is not a
    template parm object because it's still dependent.

    gcc/cp/ChangeLog:

            PR c++/98810
            * pt.c (tsubst_copy) [VIEW_CONVERT_EXPR]: Add const
            to a class non-type template argument that needs it.

    gcc/testsuite/ChangeLog:

            PR c++/98810
            * g++.dg/cpp2a/nontype-class-defarg1.C: New test.