Rollup merge of #138001 - meithecatte:privately-uninhabited, r=Nadrieril

mir_build: consider privacy when checking for irrefutable patterns

This PR fixes #137999.

Note that, since this makes the compiler reject code that was previously accepted, it will probably need a crater run.

I include a commit that factors out a common code pattern into a helper function, purely because the fact that this was repeated all over the place was bothering me. Let me know if I should split that into a separate PR instead.

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -150,9 +150,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
     /// Returns whether the given type is an enum from another crate declared `#[non_exhaustive]`.
     pub fn is_foreign_non_exhaustive_enum(&self, ty: RevealedTy<'tcx>) -> bool {
         match ty.kind() {
-            ty::Adt(def, ..) => {
-                def.is_enum() && def.is_variant_list_non_exhaustive() && !def.did().is_local()
-            }
+            ty::Adt(def, ..) => def.variant_list_has_applicable_non_exhaustive(),
             _ => false,
         }
     }