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{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE QuantifiedConstraints #-}
{-# LANGUAGE UndecidableInstances #-}
module T14833 where
data Dict c where
Dict :: c => Dict c
class (a => b) => Implies a b
instance (a => b) => Implies a b
-- Works ok
iota1 :: (() => a) => Dict a
iota1 = Dict
iota2 :: Implies () a => Dict a
iota2 = Dict
{-
[G] Implies () a
[G] (() => a) -- By superclass
[W] a
-}
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