[Bug c++/96380] [10/11/12 Regression] ICE in tree check: expected integer_cst, have view_convert_expr in get_len, at tree.h:5954

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96380

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:001c63d15e31bc0a1545426d889a0b9f671b4961

commit r12-42-g001c63d15e31bc0a1545426d889a0b9f671b4961
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Apr 20 12:16:04 2021 -0400

    c++: Don't allow defining types in enum-base [PR96380]

    In r11-2064 I made cp_parser_enum_specifier commit to tentative parse
    when seeing a '{'.  That still looks like the correct thing to do, but
    it caused an ICE-on-invalid as well as accepts-invalid.

    When we have something sneaky like this, which is broken in multiple
    ways:

      template <class>
      enum struct c : union enum struct c { e = b, f = a };

    we parse the "enum struct c" part (that's OK) and then we see that
    we have an enum-base, so we consume ':' and then parse the type-specifier
    that follows the :.  "union enum" is clearly invalid, but we're still
    parsing tentatively and we parse everything up to the ;, and then
    throw away the underlying type.  We parsed everything because we were
    tricked into parsing an enum-specifier in an enum-base of another
    enum-specifier!  Not good.

    Since the grammar for enum-base doesn't allow a defining-type-specifier,
    only a type-specifier, we should set type_definition_forbidden_message
    which fixes all the problems in this PR.

    gcc/cp/ChangeLog:

            PR c++/96380
            * parser.c (cp_parser_enum_specifier): Don't allow defining
            types in enum-base.

    gcc/testsuite/ChangeLog:

            PR c++/96380
            * g++.dg/cpp0x/enum_base4.C: New test.
            * g++.dg/cpp0x/enum_base5.C: New test.