Replaced [error_state] with [current_state_number],

which is more general, as it takes an [env].

src/Engine.ml

@@ -718,12 +718,8 @@ module Make (T : TABLE) = struct
     env1.stack == env2.stack &&
     number env1.current = number env2.current
 
-  let error_state checkpoint =
-    match checkpoint with
-    | HandlingError env ->
-        number env.current
-    | _ ->
-        invalid_arg "error_state expects HandlingError"
+  let current_state_number env =
+    number env.current
 
   (* ------------------------------------------------------------------------ *)
 

src/IncrementalEngine.ml

@@ -281,14 +281,13 @@ module type INCREMENTAL_ENGINE = sig
 
   val get: int -> 'a env -> element option
 
-  (* [error_state checkpoint] requires [checkpoint] to be of the form
-     [HandlingError env]. Out of [env], it extracts the automaton's current
-     state, and returns this state, as an integer number. (This works even if
-     the automaton's stack is empty, in which case the current state is an
-     initial state.) This number can then be used as an argument to a
-     [message] function that was generated by [menhir --compile-errors]. *)
-
-  val error_state: 'a checkpoint -> int
+  (* [current_state_number env] returns (the integer number of) the automaton's
+     current state. This works even if the automaton's stack is empty, in which
+     case the current state is an initial state. This number can be used as an
+     argument to a [message] function that was generated by [menhir
+     --compile-errors]. *)
+
+  val current_state_number: 'a env -> int
 
   (* [equal env1 env2] tells whether the parser configurations [env1] and
      [env2] are equal in the sense that the automaton's current state is

src/fancyDriver.ml

@@ -22,10 +22,10 @@ open Parser.MenhirInterpreter (* incremental API to our parser *)
 
 (* [fail] is invoked if a syntax error is encountered. *)
 
-let fail lexbuf checkpoint =
+let fail lexbuf env =
   (* The parser has suspended itself because of a syntax error. Stop.
      Find out which state the parser is currently in. *)
-  let s : int = error_state checkpoint in
+  let s : int = current_state_number env in
   (* Display a nice error message. In principle, the table found in
      [ParserMessages] should be complete, so we should obtain
      a nice message. If [Not_found] is raised, we produce a generic
@@ -43,6 +43,13 @@ let fail lexbuf checkpoint =
   (* Display our message and die. *)
   Error.error (Positions.lexbuf lexbuf) "syntax error.\n%s" message
 
+let fail lexbuf checkpoint =
+  match checkpoint with
+  | HandlingError env ->
+      fail lexbuf env
+  | _ ->
+      assert false (* this cannot happen *)
+
 (* The entry point. *)
 
 let grammar lexer lexbuf =