testsuite/tests/ghci/T18262/T18262.hs


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{-# LANGUAGE Haskell2010 #-}
{-# LANGUAGE TypeFamilies, FlexibleInstances, DataKinds, UndecidableInstances #-}

import GHC.TypeLits

data C = A | B

class Err (a :: C)

instance (TypeError ('Text "uh-oh")) => Err 'A
instance Err 'B