restore optimization in Ctype.deep_occur + remove obsolete Btype.set_…

…typeset

Changes

@@ -37,6 +37,10 @@ Working version
 - #9650, #9651: keep refactoring the pattern-matching compiler
   (Gabriel Scherer, review by Thomas Refis and Florian Angeletti)
 
+- #9994: Make Types.type_expr a private type, and abstract marking mechanism
+  (Jacques Garrigue and Takafumi Saikawa,
+   review by Gabriel Scherer and Leo White)
+
 - #10007: Driver.compile_common: when typing a .ml file, return the
   compilation unit signature (inferred or from the .cmi) in addition
   to the implementation and the coercion.

typing/btype.ml

@@ -732,7 +732,6 @@ let undo_change = function
   | Ckind  (r, v) -> r := v
   | Ccommu (r, v) -> r := v
   | Cuniv  (r, v) -> r := v
-(*  | Ctypeset (r, v) -> r := v *)
 
 type snapshot = changes ref * int
 let last_snapshot = s_ref 0
@@ -787,10 +786,6 @@ let set_kind rk k =
   log_change (Ckind (rk, !rk)); rk := Some k
 let set_commu rc c =
   log_change (Ccommu (rc, !rc)); rc := c
-(*
-let set_typeset rs s =
-  log_change (Ctypeset (rs, !rs)); rs := s
-*)
 
 let snapshot () =
   let old = !last_snapshot in

typing/ctype.ml

@@ -2105,11 +2105,10 @@ let expand_trace env trace =
 let deep_occur t0 ty =
   let rec occur_rec ty =
     let ty = repr ty in
-    if try_mark_node ty then
-      begin
-        if ty == t0 then raise Occur;
-        iter_type_expr occur_rec ty
-      end
+    if ty.level >= t0.level && try_mark_node ty then begin
+      if ty == t0 then raise Occur;
+      iter_type_expr occur_rec ty
+    end
   in
   try
     occur_rec ty; unmark_type ty; false