Rollup merge of rust-lang#89785 - nbdd0121:master, r=Mark-Simulacrum

Fix ICE when compiling nightly std/rustc on beta compiler

Fix rust-lang#89775

rust-lang#89479 renames a lot of diagnostic items, but it happens that the beta compiler assumes that there must be DefId with `rustc_diagnostic_item = "send_trait"`, causing an ICE when compiling stage 0 std or stage 1 compiler. So gate it with `cfg(bootstrap)`.

The unwrap is also removed, so that existence of the diagnostic item is not required. I ripgreped the code base and this seems the only place where `unwrap` is called on the return value of `get_diagnostic_item`.

Author: matthiaskrgr

core/src/marker.rs

@@ -30,7 +30,8 @@ use crate::hash::Hasher;
 /// [arc]: ../../std/sync/struct.Arc.html
 /// [ub]: ../../reference/behavior-considered-undefined.html
 #[stable(feature = "rust1", since = "1.0.0")]
-#[cfg_attr(not(test), rustc_diagnostic_item = "Send")]
+#[cfg_attr(all(not(test), bootstrap), rustc_diagnostic_item = "send_trait")]
+#[cfg_attr(all(not(test), not(bootstrap)), rustc_diagnostic_item = "Send")]
 #[rustc_on_unimplemented(
     message = "`{Self}` cannot be sent between threads safely",
     label = "`{Self}` cannot be sent between threads safely"