Rollup merge of rust-lang#138717 - jdonszelmann:pin-macro, r=WaffleLapkin

Add an attribute that makes the spans from a macro edition 2021, and fix pin on edition 2024 with it

Fixes a regression, see issue below. This is a temporary fix, super let is the real solution.

Closes rust-lang#138596

Author: matthiaskrgr

core/src/pin.rs

@@ -1943,6 +1943,7 @@ unsafe impl<T: ?Sized> PinCoerceUnsized for *mut T {}
 #[stable(feature = "pin_macro", since = "1.68.0")]
 #[rustc_macro_transparency = "semitransparent"]
 #[allow_internal_unstable(unsafe_pin_internals)]
+#[cfg_attr(not(bootstrap), rustc_macro_edition_2021)]
 pub macro pin($value:expr $(,)?) {
     // This is `Pin::new_unchecked(&mut { $value })`, so, for starters, let's
     // review such a hypothetical macro (that any user-code could define):

coretests/tests/pin.rs

@@ -34,6 +34,9 @@ fn pin_const() {
     }
 
     pin_mut_const();
+
+    // Check that we accept a Rust 2024 $expr.
+    std::pin::pin!(const { 1 });
 }
 
 #[allow(unused)]
@@ -81,3 +84,14 @@ mod pin_coerce_unsized {
         arg
     }
 }
+
+#[test]
+#[cfg(not(bootstrap))]
+fn temp_lifetime() {
+    // Check that temporary lifetimes work as in Rust 2021.
+    // Regression test for https://github.com/rust-lang/rust/issues/138596
+    match std::pin::pin!(foo(&mut 0)) {
+        _ => {}
+    }
+    async fn foo(_: &mut usize) {}
+}