[Bug c++/95434] ICE for CTAD in generic lambda within variadic lambda

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95434

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:cafcfcb5840b62d9fc80c12192189351e995a4f2

commit r11-6816-gcafcfcb5840b62d9fc80c12192189351e995a4f2
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed Jan 20 09:44:33 2021 -0500

    c++: Fix tsubsting CLASS_PLACEHOLDER_TEMPLATE [PR95434]

    Here, during partial instantiation of the generic lambda, we do
    tsubst_copy on the CLASS_PLACEHOLDER_TEMPLATE for U{0} which yields a
    (level-lowered) TEMPLATE_TEMPLATE_PARM rather than the corresponding
    TEMPLATE_DECL.  This later confuses do_class_deduction which expects
    that a CLASS_PLACEHOLDER_TEMPLATE is always a TEMPLATE_DECL.

    gcc/cp/ChangeLog:

            PR c++/95434
            * pt.c (tsubst) <case TEMPLATE_TYPE_PARM>: If tsubsting
            CLASS_PLACEHOLDER_TEMPLATE yields a TEMPLATE_TEMPLATE_PARM,
            adjust to its TEMPLATE_TEMPLATE_PARM_TEMPLATE_DECL.

    gcc/testsuite/ChangeLog:

            PR c++/95434
            * g++.dg/cpp2a/lambda-generic9.C: New test.