testsuite/tests/indexed-types/should_compile/T7082.hs


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{-# LANGUAGE TypeFamilies #-}
module T7082 where

import Data.Kind (Type)

class R m where
  type D m a :: Type
  type D m a = ()                -- (1)
  f :: m a -> D m a -> ()

instance R Maybe where
  -- type D Maybe a = ()         -- (2)
  f = undefined

x = f (Nothing :: Maybe Int) ()