[sledge] Implement Map.find_and_remove more directly

Summary: No need for exceptions.

Reviewed By: jvillard

Differential Revision: D18736382

fbshipit-source-id: 684bf896c

sledge/src/import/import.ml

@@ -240,17 +240,15 @@ module Map = struct
 
   let equal_m__t (module Elt : Compare_m) equal_v = equal equal_v
 
-  let find_and_remove_exn m k =
+  let find_and_remove m k =
     let found = ref None in
     let m =
       change m k ~f:(fun v ->
           found := v ;
           None )
     in
-    match !found with None -> raise Caml.Not_found | Some v -> (v, m)
-
-  let find_and_remove m k =
-    try Some (find_and_remove_exn m k) with Caml.Not_found -> None
+    let+ v = !found in
+    (v, m)
 
   let find_or_add (type data) map key ~(default : data) ~if_found ~if_added
       =

sledge/src/import/import.mli

@@ -184,7 +184,6 @@ module Map : sig
     -> ('k, 'v, 'c) t
     -> bool
 
-  val find_and_remove_exn : ('k, 'v, 'c) t -> 'k -> 'v * ('k, 'v, 'c) t
   val find_and_remove : ('k, 'v, 'c) t -> 'k -> ('v * ('k, 'v, 'c) t) option
 
   val find_or_add :