testsuite/tests/patsyn/should_compile/T8968-1.hs


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{-# LANGUAGE GADTs, KindSignatures, PatternSynonyms #-}
module ShouldCompile where

data X :: (* -> *) -> * -> * where
  Y :: f a -> X f (Maybe a)

pattern C :: a -> X Maybe (Maybe a)
pattern C x = Y (Just x)