[Bug c++/97438] New: [accepts-invalid] coroutines accepts prmomise type with both return_value() and return_void()

[Bug c++/97438] New: [accepts-invalid] coroutines accepts prmomise type with both return_value() and return_void()

[avi@cloudius-systems.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97438

            Bug ID: 97438
           Summary: [accepts-invalid] coroutines accepts prmomise type
                    with both return_value() and return_void()
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: avi@cloudius-systems.com
  Target Milestone: ---

The standard says:

[dcl.fct.def.coroutine]

6. The unqualified-ids return_­void and return_­value are looked up in the
scope of the promise type. If both are found, the program is ill-formed.


But gcc accepts such a promise type. Clang rejects it.

[Bug c++/97438] [accepts-invalid] coroutines accepts prmomise type with both return_value() and return_void()

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97438

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |iains at gcc dot gnu.org

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
testcase?

[Bug c++/97438] [accepts-invalid] coroutines accepts prmomise type with both return_value() and return_void()

[avi@cloudius-systems.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97438

--- Comment #2 from Avi Kivity <avi@cloudius-systems.com> ---
Created attachment 49379
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49379&action=edit
test case

[Bug c++/97438] [accepts-invalid] coroutines accepts prmomise type with both return_value() and return_void()

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97438

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Iain D Sandoe <iains@gcc.gnu.org>:

https://gcc.gnu.org/g:b003c4b14b3f889e6707db68d2c6545eda7a203b

commit r11-4076-gb003c4b14b3f889e6707db68d2c6545eda7a203b
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Sat Oct 17 11:21:11 2020 +0100

    coroutines: Emit error for invalid promise return types [PR97438].

    At one stage, use cases were proposed for allowing the promise
    type to contain both return_value and return_void.  That was
    not accepted into C++20, so we should reject it as per the PR.

    gcc/cp/ChangeLog:

            PR c++/97438
            * coroutines.cc (struct coroutine_info): Add a field to
            record that we emitted a promise type error.
            (coro_promise_type_found_p): Check for the case that the
            promise type contains both return_void and return_value.
            Emit an error if so, with information about the wrong
            type methods.

    gcc/testsuite/ChangeLog:

            PR c++/97438
            * g++.dg/coroutines/pr97438.C: New test.

[Bug c++/97438] [accepts-invalid] coroutines accepts prmomise type with both return_value() and return_void()

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97438

Iain Sandoe <iains at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Last reconfirmed|                            |2020-10-19
   Target Milestone|---                         |11.0
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #4 from Iain Sandoe <iains at gcc dot gnu.org> ---
fixed on master, 
the general view is that this isn't critical to back port (if there is some
pressing reason it should be then please reopen the PR).

[Bug c++/97438] [accepts-invalid] coroutines accepts prmomise type with both return_value() and return_void()

[avi@cloudius-systems.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97438

--- Comment #5 from Avi Kivity <avi@cloudius-systems.com> ---
No pressing reason to backport (for me gcc coroutines are useless anyway due to
95137)

[Bug c++/97438] [accepts-invalid] coroutines accepts prmomise type with both return_value() and return_void()

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97438

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Iain D Sandoe
<iains@gcc.gnu.org>:

https://gcc.gnu.org/g:4bca11333c274ab5d06677ed952afa097c7d3c78

commit r10-9197-g4bca11333c274ab5d06677ed952afa097c7d3c78
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Sat Oct 17 11:21:11 2020 +0100

    coroutines: Emit error for invalid promise return types [PR97438].

    At one stage, use cases were proposed for allowing the promise
    type to contain both return_value and return_void.  That was
    not accepted into C++20, so we should reject it as per the PR.

    gcc/cp/ChangeLog:

            PR c++/97438
            * coroutines.cc (struct coroutine_info): Add a field to
            record that we emitted a promise type error.
            (coro_promise_type_found_p): Check for the case that the
            promise type contains both return_void and return_value.
            Emit an error if so, with information about the wrong
            type methods.

    gcc/testsuite/ChangeLog:

            PR c++/97438
            * g++.dg/coroutines/pr97438.C: New test.

    (cherry picked from commit b003c4b14b3f889e6707db68d2c6545eda7a203b)