Auto merge of rust-lang#115012 - Zoxc:thir-check-root, r=cjgillot

Ensure that THIR unsafety check is done before stealing it

This ensures that THIR unsafety check is done before stealing it by running it on the typeck root instead of on a closure, which does nothing.

Fixes rust-lang#111520

compiler/rustc_mir_build/src/build/mod.rs

@@ -56,7 +56,8 @@ pub(crate) fn closure_saved_names_of_captured_variables<'tcx>(
 /// Construct the MIR for a given `DefId`.
 fn mir_build(tcx: TyCtxt<'_>, def: LocalDefId) -> Body<'_> {
     // Ensure unsafeck and abstract const building is ran before we steal the THIR.
-    tcx.ensure_with_value().thir_check_unsafety(def);
+    tcx.ensure_with_value()
+        .thir_check_unsafety(tcx.typeck_root_def_id(def.to_def_id()).expect_local());
     tcx.ensure_with_value().thir_abstract_const(def);
     if let Err(e) = tcx.check_match(def) {
         return construct_error(tcx, def, e);