- | WTypeVar _ => Prelude_error "top-level xi got a type variable"
- | WCoerVar _ => Prelude_error "top-level xi got a coercion variable"
+ | OK (WTypeVar _) => Prelude_error "top-level xi got a type variable"
+ | OK (WCoerVar _) => Prelude_error "top-level xi got a coercion variable"
+ | Error s => Prelude_error s