chore: reduce dependency to pin-utils

[tisonkun]

This refers to #2924.

cc @taiki-e as for "it is reasonable to remove it in v0.4", IIUC I can open a follow-up PR to remove this macro and update the corresponding related usage, only we don't mark that PR as 0.3-backport?

BTW, if there is anything I can help in backporting, please let me know. In my experience, it means opening a PR against branch 0.3 and do the same change.

[taiki-e]

Thanks for the PR!

futures-util/src/future/future/mod.rs (which is a module for Future trait related things) is not the proper place to put this macro, so perhaps it is better to create futures-util/src/macros.rs and put it there.

[taiki-e]

This should refer $crate::__private::Pin instead of ::core::pin::Pin, as pin-utils does.

[tisonkun]

Any rationale here?

I'm afraid that, as futures_util::__private is guarded by async-await flag, it would create an extra flag gate to use this name.

[taiki-e]

Any rationale here?

See rust-lang/pin-utils#26 (comment).

I'm afraid that, as futures_util::__private is guarded by async-await flag, it would create an extra flag gate to use this name.

There is no problem with removing the cfg from __private module.
That cfg just indicates who the current user is, nothing special.

[tisonkun]

OK. Let me use $crate::__private and remove the cfg.

Maybe tomorrow to trigger CI with the new toolchain that fixes the current CI failure.

[tisonkun]

@taiki-e Thanks for your review! Comments addressed.

... except the one about $crate::__private::Pin that I found the __private mod is guarded by "async-await" flag and being a bit uncertain to use.

[tisonkun]

error: unused attribute `<cfg_attr>`
   --> futures-util/src/stream/stream/mod.rs:181:1
    |
181 | #[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
note: the built-in attribute `<cfg_attr>` will be ignored, since it's applied to the macro invocation `delegate_all`
   --> futures-util/src/stream/stream/mod.rs:183:1
    |
183 | delegate_all!(
    | ^^^^^^^^^^^^
    = note: `-D unused-attributes` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(unused_attributes)]`

Doesn't seem related .. Unsure what happen.

[taiki-e]

error: unused attribute `<cfg_attr>`
   --> futures-util/src/stream/stream/mod.rs:181:1
    |
181 | #[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
note: the built-in attribute `<cfg_attr>` will be ignored, since it's applied to the macro invocation `delegate_all`
   --> futures-util/src/stream/stream/mod.rs:183:1
    |
183 | delegate_all!(
    | ^^^^^^^^^^^^
    = note: `-D unused-attributes` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(unused_attributes)]`

Doesn't seem related .. Unsure what happen.

This is rust-lang/rust#138779.