[sledge] Add Trace.fail

Reviewed By: mbouaziz

Differential Revision: D14075528

fbshipit-source-id: 0f068f063

sledge/src/trace/trace.ml

@@ -148,5 +148,13 @@ let report fmt =
   Format.fprintf fs "@\n@[<2>| " ;
   Format.kfprintf (fun fs -> Format.fprintf fs "@]" ; false) fs fmt
 
+let fail fmt =
+  Format.fprintf fs "@\n@[<2>| " ;
+  Format.kfprintf
+    (fun fs ->
+      Format.fprintf fs "@]@." ;
+      assert false )
+    fs fmt
+
 let%test_module _ =
   (module struct let () = init ~margin:70 ~config:!config () end)

sledge/src/trace/trace.mli

@@ -54,3 +54,6 @@ val flush : unit -> unit
 
 val report : ('a, Formatter.t, unit, bool) format4 -> 'a
 (** Emit a message at the current indentation level, and return [false]. *)
+
+val fail : ('a, Formatter.t, unit, _) format4 -> 'a
+(** Emit a message at the current indentation level, and [assert false]. *)