Check that type t does not contain polymorphic variables in

e : t or e :? t.

typing/typer.ml

@@ -2,7 +2,7 @@ open Cduce_loc
 open Ast
 open Ident
 open Debug
-       
+
 let (=) (x:int) y = x = y
 let (<=) (x:int) y = x <= y
 let (<) (x:int) y = x < y
@@ -1212,21 +1212,33 @@ 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.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
-       (ed,verify loc t constr)
+     if Var.Set.subset Types.(all_vars (descr t)) env.delta then begin
+	 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
+	   (ed,verify loc t constr)
+	 else
+	   raise_loc loc (Constraint(t, te))
+       end
      else
-       raise_loc loc (Constraint(t, te))
+       error loc "Polymorphic type variables cannot occur in static type-checks"
+
   | Subst (e,sl) ->
     let t = type_check env e constr precise in
     (ed,verify loc t constr)
 
   | Check (t0,e,t) ->
-    let te = type_check env e Types.any true in
-    t0 := Types.cup !t0 te;
-    (ed,verify loc (Types.cap te (Types.descr t)) constr)
+     if Var.Set.subset Types.(all_vars (descr t)) env.delta then begin
+	 let te = type_check env e Types.any true in
+	 t0 := Types.cup !t0 te;
+	 let tres = Types.cap te (Types.descr t) in
+	 if Types.is_empty tres then
+	   warning loc "This dynamic type-check will always fail";
+	 (ed, verify loc tres constr)
+       end
+     else
+       error loc "Polymorphic type variables cannot occur in dynamic type-checks"
 
   | Abstraction a ->
     (* freshen type variables from the environment to avoid capture with
@@ -1298,7 +1310,7 @@ and type_check' loc env ed constr precise = match ed with
 	in
 	let vars = Types.all_vars type_pat in
 	if not (Var.Set.subset vars env.delta) then
-	  error br.br_loc "Polymoprhic type variables cannot occur in patterns"
+	  error br.br_loc "Polymorphic type variables cannot occur in patterns"
        ) b.br_branches;
     let t = type_check env e b.br_accept true in
     let pargs = pat_list_of_expr e in