[Haskell-cafe] Explicit forall - Strange Error

[Shayan Najd Javadipour]

Hi,

I wonder why the following code doesn't typecheck in GHC 7.4.1:

{-# LANGUAGE GADTs,RankNTypes #-}data T a where T1 :: (forall b. b ->
b) -> (forall a. Int -> T a)
{- Error:
Data constructor `T1' returns type `forall a. Int -> T a'
      instead of an instance of its parent type `T a'
    In the definition of data constructor `T1'
    In the data type declaration for `T'
Failed, modules loaded: none. -}
While:


{-# LANGUAGE GADTs,RankNTypes #-}
f :: (forall b. b -> b) -> (forall a. Int -> Maybe a)f = undefined
{-
ghci> :t f
f :: (forall b. b -> b) -> Int -> Maybe a
-}


Thanks,
 Shayan
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