[Bug c++/105637] [12 Regression] Wrong overload selected in base class

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105637

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:41487bff13fa98607ab5548bc1a0dca71147a5ac

commit r12-8603-g41487bff13fa98607ab5548bc1a0dca71147a5ac
Author: Patrick Palka <ppalka@redhat.com>
Date:   Fri Jun 3 12:06:59 2022 -0400

    c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

    In non-dependent23.C below we expect the Base::foo calls to
    resolve to the second, third and fourth overloads respectively in light
    of the cv-qualifiers of 'this' in each case.  But ever since
    r12-6075-g2decd2cabe5a4f, the calls incorrectly resolve to the first
    overload at instantiation time.

    This happens because the calls to Base::foo are all deemed
    non-dependent (ever since r7-755-g23cb72663051cd made us ignore 'this'
    dependence when considering the dependence of a non-static memfn call),
    hence we end up checking the call ahead of time, using as the object
    argument a dummy object of type Base.  Since this object argument is
    cv-unqualified, the calls in turn resolve to the unqualified overload
    of baseDevice.  Before r12-6075 this incorrect result would just get
    silently discarded and we'd end up redoing OR at instantiation time
    using 'this' as the object argument.  But after r12-6075 we now reuse
    this incorrect result at instantiation time.

    This patch fixes this by making maybe_dummy_object respect the cv-quals
    of (the non-lambda) 'this' when returning a dummy object.  Thus, ahead
    of time OR using a dummy object will give us the right answer that's
    consistent with the instantiation time answer.

    An earlier version of this patch didn't handle 'this'-capturing lambdas
    correctly, which broke lambda-this22.C below.

            PR c++/105637

    gcc/cp/ChangeLog:

            * tree.cc (maybe_dummy_object): When returning a dummy
            object, respect the cv-quals of 'this' if available.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp0x/lambda/lambda-this22.C: New test.
            * g++.dg/template/non-dependent23.C: New test.

    (cherry picked from commit 44a5bd6d933d86ed988fc4695aa00f122cf83eb4)