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{-# LANGUAGE GADTs #-}
-- A program very like this triggered a kind error with GHC 6.6
module Foo where
data PatchSeq p a b where
Nil :: PatchSeq p a b
U :: p a b -> PatchSeq p a b
(:-) :: PatchSeq p a b -> PatchSeq p b c -> PatchSeq p a c
-- is_normal :: PatchSeq p a b -> Bool
is_normal Nil = True
is_normal (U _) = True
is_normal (U _ :- _) = True
is_normal _ = False
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