This example is derived from code in my application. It works, but I can't add a signature to it. In other places it is preventing some code from compiling at all.

{-# LANGUAGE KindSignatures, MultiParamTypeClasses, RankNTypes #-}
{-# OPTIONS -Wall #-}
module Test where

class C t1 t2 m where method :: Int -> m t2

f :: forall t1 t2 (m :: * -> *). C t1 t2 m => Int -> m t2
f x = method x