add rustc_macro_edition_2021

Author: jdonszelmann

Diff for: 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):

Diff for: coretests/tests/pin.rs

@@ -81,3 +81,16 @@ mod pin_coerce_unsized {
         arg
     }
 }
+
+#[test]
+fn spans_2021() {
+    // Check that we accept a Rust 2024 $expr.
+    std::pin::pin!(const { 1 });
+
+    // Check that temporary lifetimes work as in Rust 2021.
+    match std::pin::pin!(foo(&mut 0)) {
+        _f => {}
+    }
+}
+
+async fn foo(_: &mut usize) {}