[2026-03 LWG Motion 35] P3927R2 task_scheduler support for parallel bulk execution

[jensmaurer]

Fixes NB US 238-368 (C++26 CD).

Fixes #8869

Also fixes cplusplus/papers#2600
Also fixes cplusplus/nbballot#943

[ericniebler]

looks good. thanks!

[jwakely]

There's a stray x in the pull request.

There are two places where the paper says that ts-domain::transform_sender is exposition-only, which are not in the pull request. But if it's exposition-only, why isn't it called transform-sender instead? If its name needs to be transform_sender then it's not exposition only, and the pull request is correct. I don't know.

[tkoeppe]

There are two places where the paper says that ts-domain::transform_sender is exposition-only, which are not in the pull request. But if it's exposition-only, why isn't it called transform-sender instead? If its name needs to be transform_sender then it's not exposition only, and the pull request is correct. I don't know.

Since ts-domain itself is an exposition-only class, I don't think it's observable whether its members are also exposition-only, and we don't need to also annotate members. E.g. the members of backend-for (added in the same paper) are also not annotated. I think that's fine, I don't see what else it could mean.