[Bug c++/100079] [9/10/11 Regression] Non-type template parameter, itself a nested template, rejected with internal error

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100079

--- Comment #4 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:89c863488bc8c7315596bcb753173aa2fd8be727

commit r11-8207-g89c863488bc8c7315596bcb753173aa2fd8be727
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Apr 14 17:27:19 2021 -0400

    c++: C++20 class NTTP trailing zero-init [PR100079]

    The new testcase was breaking because constexpr evaluation was simplifying
    Bar{Baz<42>{}} to Bar{empty}, but then we weren't treating them as
    equivalent.  Poking at this revealed that the code for eliding trailing
    zero-initialization in class non-type template argument mangling was pretty
    broken, including the test, mangle71.

    I dealt with the FIXME to support RANGE_EXPR, and fixed the confusion
    between a list-initialized temporary mangled as written (i.e. in the
    signature of a function template) and a template parameter object mangled
as
    the value representation of the object.  I'm distinguishing between these
    using COMPOUND_LITERAL_P.  A later patch will adjust the use of
    COMPOUND_LITERAL_P to be more useful for this distinction, but it works now
    for distinguishing these cases in mangling.

    gcc/cp/ChangeLog:

            PR c++/100079
            * cp-tree.h (first_field): Declare.
            * mangle.c (range_expr_nelts): New.
            (write_expression): Improve class NTTP mangling.
            * pt.c (get_template_parm_object): Clear TREE_HAS_CONSTRUCTOR.
            * tree.c (zero_init_expr_p): Improve class NTTP handling.
            * decl.c: Adjust comment.

    gcc/testsuite/ChangeLog:

            PR c++/100079
            * g++.dg/abi/mangle71.C: Fix expected mangling.
            * g++.dg/abi/mangle77.C: New test.
            * g++.dg/cpp2a/nontype-class-union1.C: Likewise.
            * g++.dg/cpp2a/nontype-class-equiv1.C: Removed.
            * g++.dg/cpp2a/nontype-class44.C: New test.