testsuite/tests/ghc-regress/indexed-types/should_compile/Simple9.hs


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{-# LANGUAGE TypeFamilies #-}

module Simple9 where

-- The test succeeds with
--
-- type family F a b
-- type instance F () b = Maybe b

type family F a :: * -> *
type instance F () = Maybe

type family G a
type instance G (Maybe a) = Int

foo :: G (F () a) -> Int
foo x = x