[Bug c++/91706] [9/10/11/12 Regression] ICE: tree check: expected class 'type', have 'exceptional' (error_mark) in equate_type_number_to_die, at dwarf2out.c:5782

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91706

--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:46c1a9f6d03ab444b42c41067597e3fbfba38486

commit r11-8524-g46c1a9f6d03ab444b42c41067597e3fbfba38486
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Apr 16 11:13:40 2021 -0400

    c++: alias with same name as base fn [PR91706]

    This is a bit complex.  Looking up c<T> in the definition of D::c finds
    C::c, OK.  Looking up c in the definition of E finds D::c, OK.  Since the
    alias is not dependent, we strip it from the template argument, leaving

    using E = A<decltype(c<T>())>;

    where 'c' still refers to C::c.  But instantiating E looks up 'c' again and
    finds D::c, which isn't a function, and sadness ensues.

    I think the bug here is looking up 'c' in D at instantiation time; the
    declaration we found before is not dependent.  This seems to happen because
    baselink_for_fns gets BASELINK_BINFO wrong; it is supposed to be the base
    where lookup found the functions, C in this case.

    gcc/cp/ChangeLog:

            PR c++/91706
            * semantics.c (baselink_for_fns): Fix BASELINK_BINFO.

    gcc/testsuite/ChangeLog:

            PR c++/91706
            * g++.dg/template/lookup17.C: New test.