[Bug c++/108606] [13 Regression] ICE in potential_constant_expression_1 with friend function declaration inside a local class of a generic/templated lambda

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108606

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:b222e725f53231a0bd9799ca93892a79d592a5f3

commit r13-6387-gb222e725f53231a0bd9799ca93892a79d592a5f3
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Mar 1 10:22:59 2023 +0100

    c++: Don't recurse on DECL_INITIAL for DECL_EXPR on non-VAR_DECLs
[PR108606]

    The r13-2965-g73d9b0e5947e16 change changed the line touched in this patch
    from
          return RECUR (tmp, want_rval);
    to
          return RECUR (DECL_INITIAL (tmp), want_rval);
    This is on DECL_EXPR handling code, where tmp can be lots of different
    trees and DECL_INITIAL unfortunately also means different things on
    different trees.
    It is the initializer on VAR_DECL, DECL_ARG_TYPE on PARM_DECLs (though
    those are unlikely to have DECL_EXPRs), for FUNCTION_DECLs the body,
    ..., USING_DECL_DECLS on USING_DECLs and DECL_FRIENDLIST on TYPE_DECLs.

    The testcase below ICEs because we have a DECL_EXPR for TYPE_DECL
    which has non-NULL DECL_FRIENDLIST and we certainly can't recurse on
    the friend list.

    The following patch will RECUR on DECL_INITIAL only for VAR_DECLs and
    for anything else just return true.

    2023-03-01  Jakub Jelinek  <jakub@redhat.com>

            PR c++/108606
            * constexpr.cc (potential_constant_expression_1) <case DECL_EXPR>:
            Only recurse on DECL_INITIAL (tmp) if tmp is a VAR_DECL, otherwise
            just return true.

            * g++.dg/cpp1y/pr108606.C: New test.