[Bug c++/122310] Compilation error when including before importing

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122310

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-15 branch has been updated by Nathaniel Shead
<nshead@gcc.gnu.org>:

https://gcc.gnu.org/g:fc900b25fa353849649a6a221ead2da580408820

commit r15-10460-gfc900b25fa353849649a6a221ead2da580408820
Author: Nathaniel Shead <nathanieloshead@gmail.com>
Date:   Sat Oct 18 23:43:14 2025 +1100

    c++/modules: Use containing type as key for all member lambdas [PR122310]

    The ICE in the linked PR occurs because we first stream the lambda type
    before its keyed decl has been streamed, but the key decl's type depends
    on the lambda.  And so when streaming the key decl to check for an
    existing decl to merge with, merging the key decl itself crashes because
    its type has only been partially streamed.

    This patch fixes the issue by generalising the existing FIELD_DECL
    handling to any class member using the outermost containing TYPE_DECL as
    its key type.  This way we can guarantee that the key decl has been
    streamed before the lambda type is otherwise needed.

            PR c++/122310

    gcc/cp/ChangeLog:

            * module.cc (get_keyed_decl_scope): New function.
            (trees_out::get_merge_kind): Use it.
            (trees_out::key_mergeable): Use it.
            (maybe_key_decl): Key to the containing type for all members.

    gcc/testsuite/ChangeLog:

            * g++.dg/modules/lambda-12.h: New test.
            * g++.dg/modules/lambda-12_a.H: New test.
            * g++.dg/modules/lambda-12_b.C: New test.

    Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
    Reviewed-by: Jason Merrill <jason@redhat.com>
    (cherry picked from commit 8212abbeffa69f143808e126f40c67f3eb7e7844)