typeEnvClasses  env = [cl | tc <- typeEnvTyCons env,
                            Just cl <- [tyConClass_maybe tc]]
typeEnvClasses  env = [cl | tc <- typeEnvTyCons env,
                            Just cl <- [tyConClass_maybe tc]]
typeEnvClasses  env = [cl | tc <- typeEnvTyCons env,
                            Just cl <- [tyConClass_maybe tc]]