Improve completeness of xhp attribute check

Summary: Partial undo of {D40796712}, uses the common facility for like types instead of custom logic, improves completeness for compound types.

Differential Revision: D45938412

fbshipit-source-id: 0722459a95a5c240a4823471a529ef7e0cdac874

hphp/hack/src/typing/tast_check/xhp_required_check.ml

@@ -34,6 +34,7 @@ let collect_attrs_from_ty_sid ?(include_optional = false) env add bag sid =
 let rec collect_attrs_from_ty env set ty =
   let (_, ty) = Env.expand_type env ty in
   let tenv = Tast_env.tast_env_as_typing_env env in
+  let ty = Typing_utils.strip_dynamic tenv ty in
   match get_node ty with
   | Tunion tys ->
     (* Filter out dynamic, as we conservatively assume that anything dynamic