Rollup merge of #103800 - danielhenrymantilla:stabilize-pin-macro, r=dtolnay

Stabilize `::{core,std}::pin::pin!`

As discussed [over here](https://github.com/rust-lang/rust/issues/93178#issuecomment-1295843548), it looks like a decent time to stabilize the `pin!` macro.

### Public API

```rust
// in module `core::pin`

/// API: `fn pin<T>($value: T) -> Pin<&'local mut T>`
pub macro pin($value:expr $(,)?) {
    …
}
```

  - Tracking issue: #93178

(now all this needs is an FCP by the proper team?)

library/core/src/pin.rs

@@ -622,9 +622,8 @@ impl<P: Deref> Pin<P> {
     /// that the closure is pinned.
     ///
     /// The better alternative is to avoid all that trouble and do the pinning in the outer function
-    /// instead (here using the unstable `pin` macro):
+    /// instead (here using the [`pin!`][crate::pin::pin] macro):
     /// ```
-    /// #![feature(pin_macro)]
     /// use std::pin::pin;
     /// use std::task::Context;
     /// use std::future::Future;
@@ -1026,7 +1025,6 @@ impl<P, U> DispatchFromDyn<Pin<U>> for Pin<P> where P: DispatchFromDyn<U> {}
 /// ### Basic usage
 ///
 /// ```rust
-/// #![feature(pin_macro)]
 /// # use core::marker::PhantomPinned as Foo;
 /// use core::pin::{pin, Pin};
 ///
@@ -1044,7 +1042,6 @@ impl<P, U> DispatchFromDyn<Pin<U>> for Pin<P> where P: DispatchFromDyn<U> {}
 /// ### Manually polling a `Future` (without `Unpin` bounds)
 ///
 /// ```rust
-/// #![feature(pin_macro)]
 /// use std::{
 ///     future::Future,
 ///     pin::pin,
@@ -1083,7 +1080,7 @@ impl<P, U> DispatchFromDyn<Pin<U>> for Pin<P> where P: DispatchFromDyn<U> {}
 /// ### With `Generator`s
 ///
 /// ```rust
-/// #![feature(generators, generator_trait, pin_macro)]
+/// #![feature(generators, generator_trait)]
 /// use core::{
 ///     ops::{Generator, GeneratorState},
 ///     pin::pin,
@@ -1126,7 +1123,6 @@ impl<P, U> DispatchFromDyn<Pin<U>> for Pin<P> where P: DispatchFromDyn<U> {}
 /// The following, for instance, fails to compile:
 ///
 /// ```rust,compile_fail
-/// #![feature(pin_macro)]
 /// use core::pin::{pin, Pin};
 /// # use core::{marker::PhantomPinned as Foo, mem::drop as stuff};
 ///
@@ -1168,7 +1164,7 @@ impl<P, U> DispatchFromDyn<Pin<U>> for Pin<P> where P: DispatchFromDyn<U> {}
 /// constructor.
 ///
 /// [`Box::pin`]: ../../std/boxed/struct.Box.html#method.pin
-#[unstable(feature = "pin_macro", issue = "93178")]
+#[stable(feature = "pin_macro", since = "CURRENT_RUSTC_VERSION")]
 #[rustc_macro_transparency = "semitransparent"]
 #[allow_internal_unstable(unsafe_pin_internals)]
 pub macro pin($value:expr $(,)?) {

library/core/tests/lib.rs

@@ -48,7 +48,6 @@
 #![feature(is_sorted)]
 #![feature(layout_for_ptr)]
 #![feature(pattern)]
-#![feature(pin_macro)]
 #![feature(sort_internals)]
 #![feature(slice_take)]
 #![feature(slice_from_ptr_range)]

src/tools/miri/tests/pass/issues/issue-miri-2068.rs

@@ -1,5 +1,3 @@
-#![feature(pin_macro)]
-
 use core::future::Future;
 use core::pin::Pin;
 use core::task::{Context, Poll};

src/tools/miri/tests/pass/stacked-borrows/future-self-referential.rs

@@ -1,5 +1,3 @@
-#![feature(pin_macro)]
-
 use std::future::*;
 use std::marker::PhantomPinned;
 use std::pin::*;

tests/ui/pin-macro/cant_access_internals.rs

@@ -1,5 +1,4 @@
 // edition:2018
-#![feature(pin_macro)]
 
 use core::{
     marker::PhantomPinned,

tests/ui/pin-macro/cant_access_internals.stderr

@@ -1,5 +1,5 @@
 error[E0658]: use of unstable library feature 'unsafe_pin_internals'
-  --> $DIR/cant_access_internals.rs:12:15
+  --> $DIR/cant_access_internals.rs:11:15
    |
 LL |     mem::take(phantom_pinned.pointer);
    |               ^^^^^^^^^^^^^^^^^^^^^^

tests/ui/pin-macro/lifetime_errors_on_promotion_misusage.rs

@@ -1,5 +1,4 @@
 // edition:2018
-#![feature(pin_macro)]
 
 use core::{
     convert::identity,

tests/ui/pin-macro/lifetime_errors_on_promotion_misusage.stderr

@@ -1,5 +1,5 @@
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/lifetime_errors_on_promotion_misusage.rs:12:35
+  --> $DIR/lifetime_errors_on_promotion_misusage.rs:11:35
    |
 LL |     let phantom_pinned = identity(pin!(PhantomPinned));
    |                                   ^^^^^^^^^^^^^^^^^^^ - temporary value is freed at the end of this statement
@@ -13,7 +13,7 @@ LL |     stuff(phantom_pinned)
    = note: this error originates in the macro `pin` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/lifetime_errors_on_promotion_misusage.rs:19:30
+  --> $DIR/lifetime_errors_on_promotion_misusage.rs:18:30
    |
 LL |     let phantom_pinned = {
    |         -------------- borrow later stored here