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

Fix ICE when compiling nightly std/rustc on beta compiler

Fix #89775

#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`.

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -704,7 +704,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 .filter_map(|lang_item| self.tcx.lang_items().require(*lang_item).ok())
                 .collect();
 
-        never_suggest_borrow.push(self.tcx.get_diagnostic_item(sym::Send).unwrap());
+        if let Some(def_id) = self.tcx.get_diagnostic_item(sym::Send) {
+            never_suggest_borrow.push(def_id);
+        }
 
         let param_env = obligation.param_env;
         let trait_ref = poly_trait_ref.skip_binder();

library/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"