2 files changed, 14 insertions, 0 deletions
diff --git a/lib/util.ml b/lib/util.ml
index c2d290714b..fb968cc64f 100644
--- a/lib/util.ml
+++ b/lib/util.ml
@@ -34,6 +34,12 @@ let is_blank = function
   | ' ' | '\r' | '\t' | '\n' -> true
   | _ -> false
 
+module Empty =
+struct
+  type t
+  let abort (x : t) = assert false
+end
+
 (* Strings *)
 
 module String : CString.ExtS = CString
diff --git a/lib/util.mli b/lib/util.mli
index 33812c2004..209f64c2f6 100644
--- a/lib/util.mli
+++ b/lib/util.mli
@@ -34,6 +34,14 @@ val is_digit : char -> bool
 val is_ident_tail : char -> bool
 val is_blank : char -> bool
 
+(** {6 Empty type} *)
+
+module Empty :
+sig
+  type t
+  val abort : t -> 'a
+end
+
 (** {6 Strings. } *)
 
 module String : CString.ExtS