[Bug c++/119378] [12/13/14 Regression] Nested template class friend of template class produces "internal compiler error: unexpected expression ‘T’ of kind template_parm_index"

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119378

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-14 branch has been updated by Patrick Palka
<ppa...@gcc.gnu.org>:

https://gcc.gnu.org/g:d025b6880cde2cb2063b4d34546cdd70e5526e74

commit r14-11434-gd025b6880cde2cb2063b4d34546cdd70e5526e74
Author: Patrick Palka <ppa...@redhat.com>
Date:   Sat Mar 22 10:18:07 2025 -0400

    c++: ICE w/ dependently scoped template friend [PR119378]

    Here we ICE during instantiation of the dependently scoped template
    friend

      template<int N>
      struct<class T>
      friend class A<N>::B;

    ultimately because processing_template_decl isn't set during
    substitution into the A<N> scope.  Since it's naturally a partial
    substitution, we need to make sure the flag is set.

    For GCC 15, this is already fixed similarly by r15-123.

            PR c++/119378

    gcc/cp/ChangeLog:

            * pt.cc (tsubst) <case UNBOUND_CLASS_TEMPLATE>: Set
            processing_template_decl when substituting the context.

    gcc/testsuite/ChangeLog:

            * g++.dg/template/friend85.C: New test.

    Reviewed-by: Jason Merrill <ja...@redhat.com>