Rollup merge of #85934 - tmiasko:is-union, r=jackh726

Add `Ty::is_union` predicate

compiler/rustc_mir/src/transform/check_consts/validation.rs

@@ -752,12 +752,8 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
             | ProjectionElem::Field(..)
             | ProjectionElem::Index(_) => {
                 let base_ty = Place::ty_from(place_local, proj_base, self.body, self.tcx).ty;
-                match base_ty.ty_adt_def() {
-                    Some(def) if def.is_union() => {
-                        self.check_op(ops::UnionAccess);
-                    }
-
-                    _ => {}
+                if base_ty.is_union() {
+                    self.check_op(ops::UnionAccess);
                 }
             }
         }