ScopedTypeVariables

ScopedTypeVariablesTest.hs

--#This code blows up
myFunction :: Ord a => [a] -> [a]
myFunction inputArray = reversedArray where
  reversedArray :: Ord a => [a]
  reversedArray = reverse inputArray

main :: IO ()
main = print $ myFunction [1,2,3]

--#Below code works
{-# LANGUAGE ScopedTypeVariables #-}

myFunction :: forall a. Ord a => [a] -> [a]
myFunction inputArray = reversedArray where
  reversedArray :: Ord a => [a]
  reversedArray = reverse inputArray

main :: IO ()
main = print $ myFunction [1,2,3]