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{-# LANGUAGE ViewPatterns #-}
{-# OPTIONS_GHC -fno-warn-overlapping-patterns #-}
module T3342 where
data F = FT String [F]
data G = GX F F | GY
spec :: F -> G
spec (FT "X" [t1, t2]) = GX t1 t2
spec _ = GY
-- walk :: F -> F
walk (spec -> GX _ t2) = walk t2
walk t@(FT _ _) = t
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