Incorrect behaviour when resolving associated type of an interface

[casper-pragma]

I have defined the following interface:

interface Failable c where
  Failure : Type
  initWithFailure : Failure -> c

Then I proceeded to create an implementation:

Failable (Maybe a) where
  Failure = ({T:Type} -> T)
  initWithFailure _ = Nothing

This was accepted by the compiler, but when I tried to use it in the following manner...

main :: IO ()
main = do
  let smth : ({K:Type} -> Maybe K) = initWithFailure ()

...the compiler said that there is a type mismatch between () and Failure.

This not suppose to happen, right?