[Bug c++/96316] New: [coroutines] Promise parameter preview - looking for promise constructor with implicit lambda argument

[Bug c++/96316] New: [coroutines] Promise parameter preview - looking for promise constructor with implicit lambda argument

[skdkksfadkadkk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96316

            Bug ID: 96316
           Summary: [coroutines] Promise parameter preview - looking for
                    promise constructor with implicit lambda argument
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: skdkksfadkadkk at gmail dot com
  Target Milestone: ---

Created attachment 48926
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48926&action=edit
Code example

The feature "promise parameter preview" works wrong with lambda function,
because lambda also has an implicit argument, so compiler tries to find promise
type constructor, that has this implicit argument with other explicit lambda
arguments.

[Bug c++/96316] [coroutines] Promise parameter preview - looking for promise constructor with implicit lambda argument

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96316

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #1 from Iain Sandoe <iains at gcc dot gnu.org> ---

In fact, this is correct operation; decided jointly between the implementors
during WG21 sessions as intended behaviour.

Essentially, the lambda object pointer is treated the same way as the 'this'
pointer for a regular method (so that the traits, parameter preview and
allocator lookup are all passed a reference to the object).

At present, not sure if clang has made the amendment - but MSVC and GCC should
both comply with the intention.

If you believe that there's some other issue with this please reopen.

[Bug c++/96316] [coroutines] Promise parameter preview - looking for promise constructor with implicit lambda argument

[skdkksfadkadkk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96316

--- Comment #2 from skdkksfadkadkk at gmail dot com ---
Got it, thanks. I was confused by clang's behavior because it doesn't require
implicit argument, pointing on lambda instance.
One more question: how this implicit argument should be declared properly in
promise constructor - what type this argument should be?
For now i only see the way to declare it as a template, but may be there is
another way to declare it's type explicitly, without templates?