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kgadek/playground.hs

Created January 29, 2015 15:54
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How to force typechecker not to instantiate `id` ?
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playground.hs
{-# LANGUAGE RankNTypes, ImpredicativeTypes, ScopedTypeVariables #-}
main = return ()
data Lam f = Lam f
helper =
let a = Lam undefined :: Lam (forall a. a -> a)
--b = Lam id :: Lam (forall a. a -> a)
--c = Lam id2 :: Lam (forall a. a -> a)
in ()
id2 :: forall a. a -> a
id2 x = x
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