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🔥 OVERLAPPABLE.

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This commit is contained in:
Rob Rix 2019-10-08 15:37:52 -04:00
parent 711ec1957d
commit 3334ec81d3
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1 changed files with 3 additions and 6 deletions
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9
semantic-tags/src/AST/Element.hs
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@ -40,18 +40,15 @@ type family (a :: Side) <> (b :: Side) :: Side where
class Element' (side :: Side) sub sup where class Element' (side :: Side) sub sup where
prj' :: sup a -> Maybe (sub a) prj' :: sup a -> Maybe (sub a)
instance {-# OVERLAPPABLE #-} instance Element' 'Here t t where
Element' 'Here t t where
prj' = Just prj' = Just
instance {-# OVERLAPPABLE #-} instance Element t l
Element t l
=> Element' 'L t (l :+: r) where => Element' 'L t (l :+: r) where
prj' (L1 l) = prj l prj' (L1 l) = prj l
prj' _ = Nothing prj' _ = Nothing
instance {-# OVERLAPPABLE #-} instance Element t r
Element t r
=> Element' 'R t (l :+: r) where => Element' 'R t (l :+: r) where
prj' (R1 r) = prj r prj' (R1 r) = prj r
prj' _ = Nothing prj' _ = Nothing