[Bug c++/104981] [coroutines] Internal compiler error when promise object's constructor takes a base class of the object parameter

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104981

--- Comment #7 from GCC 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:7c5a9bf1d206fe20cb050200d4a30f11c76b1b19

commit r15-2210-g7c5a9bf1d206fe20cb050200d4a30f11c76b1b19
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon Jul 22 21:30:49 2024 -0400

    c++/coroutines: correct passing *this to promise type [PR104981]

    When passing *this to the promise type ctor (or to its operator new)
    (as per [dcl.fct.def.coroutine]/4), we add an explicit cast to lvalue
    reference.  But this is unnecessary since *this is already always an
    lvalue.  And doing so means we need to call convert_from_reference
    afterward to lower the reference expression to an implicit dereference,
    which we're currently neglecting to do and which causes overload
    resolution to get confused when computing argument conversions.

    So this patch removes this unneeded reference cast when passing *this
    to the promise ctor, and removes both the cast and implicit deref when
    passing *this to operator new, for consistency.  While we're here, use
    cp_build_fold_indirect_ref instead of directly building INDIRECT_REF.

            PR c++/104981
            PR c++/115550

    gcc/cp/ChangeLog:

            * coroutines.cc (morph_fn_to_coro): Remove unneeded calls
            to convert_to_reference and convert_from_reference when
            passing *this.  Use cp_build_fold_indirect_ref instead
            of directly building INDIRECT_REF.

    gcc/testsuite/ChangeLog:

            * g++.dg/coroutines/pr104981-preview-this.C: New test.
            * g++.dg/coroutines/pr115550-preview-this.C: New test.

    Reviewed-by: Iain Sandoe <iain@sandoe.co.uk>
    Reviewed-by: Jason Merrill <jason@redhat.com>