Untitled

http://stackoverflow.com/questions/26439889/extension-overloadedstring-doesnt-fully-infer-isstring-why-or-what-am-i-missi

{-# LANGUAGE GADTs #-}
data A
data B a where 
    Foo :: a -> B A

main = let x = Foo "ok" in putStrLn "YAY!"

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE GADTs #-}
data A
data B a where 
    Foo :: a -> B A

main = let x = Foo "ok" in putStrLn "YAY!"