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{-# OPTIONS_GHC -Wredundant-constraints -dsuppress-uniques #-}
{-# LANGUAGE DefaultSignatures, InstanceSigs #-}
module M ( f ) where
-- Redundant constraint
f :: Eq a => a -> ()
f _ = ()
-- Redundant constraint in expression signature
g _ = (\x -> ()) :: Eq a => a -> ()
-- GHC highlights more than necessary
h :: (Eq a, Ord b) => a -> b -> b
h _ b
| b <= b = b
| otherwise = b
-- Redundant constraint in specialize pragma.
-- Also generates an unrelated warning:
-- > Forall'd constraint ‘Eq a’ is not bound in RULE lhs
{-# SPECIALISE spec :: Eq a => a -> Int -> Int #-}
spec :: Ord b => a -> b -> b
spec _ b
| b <= b = b
| otherwise = b
class Foo a where
foo :: [a]
-- Redundant constraint in default method
default foo :: Show a => [a]
foo = []
class Bar a where
bar :: Ord b => a -> b -> a
instance Bar Int where
-- Redundant Constraint in Instance Signature
bar :: (Eq b, Ord b) => Int -> b -> Int
bar n _ = n
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