Can we drop reexport pin_mut macro?

[tisonkun]

Currently, futures-util reexport pin_utils::pin_mut! and it is reexported in the facade futures also:

futures-rs/futures-util/src/lib.rs

Line 26 in 048995a

pub use pin_utils::pin_mut;

futures-rs/futures/src/lib.rs

Line 122 in 048995a

pub use futures_util::pin_mut;

pin-utils::pin_mut has been deprecated in favor of core lib's core::pin::pin! since 1.68. However, the semantic of pin_mut is subtly different from pin. IIUC -

let object = ...;
pin_mut!(object);

// is equal to

let object = ...;
let object = pin!(object);

(and pin_mut! support pin multiple values)

I wonder if we can drop reexport pin_mut macro so that we don't depend on a deprecated lib in the next breaking release (0.4), or we should wrap a pin_mut! based on core::pin::pin:

#[macro_export]
macro_rules! pin_mut {
    ($($x:ident),* $(,)?) => { $(
        let mut $x = core::pin::pin!($x);
    )* }
}

Or we just do nothing and keep the current code forever?

Another related question is whether we could replace futures_core::ready! with core::task::ready! when the MSRV is bumped beyond 1.64.

cc @taiki-e since we have related discussions at #2901 and on zulip.

[taiki-e]

I think it is reasonable to remove it in v0.4, but I don't think v0.3 will do anything since dropping it is a breaking change. However, it may be okay to inline it to remove dependency on pin-utils.