Renaming of the three modes.

src/Unbound.ml

 type 'env mode =
-  | OutsideRec          (* updating [current] and visiting [outer] subterms *)
+  | ExtendAndVisit          (* updating [current] and visiting [outer] subterms *)
                         (* we are outside [rec] and outside [repeated] *)
-  | InsideRecDiscovery  (* updating [current] and doing nothing else; embedded subterms not visited *)
+  | ExtendNoVisit  (* updating [current] and doing nothing else; embedded subterms not visited *)
                         (* we are under [rec] in the discovery phase *)
-  | InsideRecVisit      (* [current] not updated; [inner] is [current]; embedded subterms visited *)
+  | LookupAndVisit      (* [current] not updated; [inner] is [current]; embedded subterms visited *)
                         (* we are either under [rec] in the visit phase, or under [repeated] *)
 
 type 'env penv = {
-    current: 'env ref; (* threaded left to right *)
+    current: 'env ref; (* threaded left to right; do NOT use a mutable field! *)
     outer: 'env; (* sent down only *)
     mode: 'env mode;
   }
@@ -49,7 +49,7 @@ class virtual ['self] libmap = object (self : 'self)
     ('env penv -> 'p1 -> 'p2) ->
     'env -> 'p1 abstraction -> 'p2 abstraction
   = fun visit_p env p1 ->
-      let penv = { current = ref env; outer = env; mode = OutsideRec } in
+      let penv = { current = ref env; outer = env; mode = ExtendAndVisit } in
       visit_p penv p1
 
   method private visit_outer: 'env 't1 't2 .
@@ -57,10 +57,10 @@ class virtual ['self] libmap = object (self : 'self)
     'env penv -> 't1 outer -> 't2 outer
   = fun visit_t penv t1 ->
       match penv.mode with
-      | OutsideRec
-      | InsideRecVisit ->
+      | ExtendAndVisit
+      | LookupAndVisit ->
           visit_t penv.outer t1
-      | InsideRecDiscovery ->
+      | ExtendNoVisit ->
           (* An [outer] subterm is NOT visited in discovery mode. *)
           Obj.magic ()
 
@@ -69,14 +69,14 @@ class virtual ['self] libmap = object (self : 'self)
     'env penv -> 'bn1 binder -> 'bn2 binder
   = fun _ penv x1 ->
       match penv.mode with
-      | OutsideRec
-      | InsideRecDiscovery ->
+      | ExtendAndVisit
+      | ExtendNoVisit ->
           let current = penv.current in
           let env = !current in
           let x2, env = self#extend x1 env in
           current := env;
           x2
-      | InsideRecVisit ->
+      | LookupAndVisit ->
           (* The environment should not be extended when in visit mode.
              It has been extended already during the discovery phase. *)
           self#lookup x1 !(penv.current)
@@ -87,15 +87,15 @@ class virtual ['self] libmap = object (self : 'self)
     'env penv -> ('p1, 'q1) rebind -> ('p2, 'q2) rebind
   = fun visit_p visit_q penv (p1, q1) ->
       match penv.mode with
-      | OutsideRec ->
+      | ExtendAndVisit ->
           let p2 = visit_p penv p1 in
           (* Copy [current] into [outer]. This changes the meaning of [outer]
              in the right-hand side of [rebind]. *)
           let penv = { penv with outer = !(penv.current) } in
           let q2 = visit_q penv q1 in
           p2, q2
-      | InsideRecDiscovery
-      | InsideRecVisit ->
+      | ExtendNoVisit
+      | LookupAndVisit ->
           (* [rebind] forbidden under [rec] and [repeated] *)
           assert false
 
@@ -116,11 +116,11 @@ class virtual ['self] libmap = object (self : 'self)
     'env penv -> 't1 inner -> 't2 inner
   = fun visit_t penv t1 ->
       match penv.mode with
-      | InsideRecDiscovery ->
+      | ExtendNoVisit ->
           (* An [inner] subterm is NOT visited in discovery mode. *)
           Obj.magic ()
-      | OutsideRec
-      | InsideRecVisit ->
+      | ExtendAndVisit
+      | LookupAndVisit ->
           visit_t !(penv.current) t1
 
   method private visit_recursive: 'env 'p1 'p2 .
@@ -128,16 +128,16 @@ class virtual ['self] libmap = object (self : 'self)
     'env penv -> 'p1 recursive -> 'p2 recursive
   = fun visit_p penv p1 ->
       match penv.mode with
-      | OutsideRec ->
+      | ExtendAndVisit ->
           (* Discovery phase. Result is discarded (fortunately, since we have used
              [magic] to produce it, and it is entirely meaningless). *)
-          let penv = { penv with mode = InsideRecDiscovery } in
+          let penv = { penv with mode = ExtendNoVisit } in
           let _ = visit_p penv p1 in
           (* [!current] becomes [inner] *)
-          let penv = { penv with mode = InsideRecVisit } in
+          let penv = { penv with mode = LookupAndVisit } in
           visit_p penv p1
-      | InsideRecDiscovery
-      | InsideRecVisit ->
+      | ExtendNoVisit
+      | LookupAndVisit ->
           (* [rec] forbidden under [rec] or [repeated] *)
           assert false
 
@@ -145,7 +145,7 @@ class virtual ['self] libmap = object (self : 'self)
     ('env penv -> 'p1 -> 'p2) ->
     'env penv -> 'p1 repeated -> 'p2 repeated
   = fun visit_p penv p1 ->
-      let penv = { penv with mode = InsideRecVisit } in
+      let penv = { penv with mode = LookupAndVisit } in
       visit_p penv p1
 
 end