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


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{-# LANGUAGE TypeFamilies #-}

module Col  where 

type family Elem c

type instance Elem [e] = e

class Col c where
 singleton :: Elem c -> c
 add :: c -> Elem c -> c

instance Col [e] where
 singleton = \x -> [x]
 add = flip (:)