Correctly refresh the type of the variables of t in a Forget(e,t) expression to

avoid a clash with variables in e.

typing/typer.ml

@@ -1211,7 +1211,7 @@ let rec type_check env e constr precise =
 
 and type_check' loc env ed constr precise = match ed with
   | Forget (e,t) ->
-     let t = Types.descr t in
+     let t = Types.Subst.freshen env.delta (Types.descr t) in
      let te = type_check env e Types.any true in
      let delta = Var.Set.cup (Types.all_vars t) env.delta in
      if Type_tallying.is_squaresubtype delta te t then