File: PatternSynonyms2.hs.prettyprinter.golden

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{-# LANGUAGE PatternSynonyms, ScopedTypeVariables, KindSignatures
  #-}
module Foo (pattern Single) where

pattern Single x <- [x]
  where Single 4 = [x]
        Single 5 = [x]

pattern Double x = [x]

single :: [a] -> Maybe a
single (Single x) = Just x
single _ = Nothing