[Haskell-cafe] Type synonym application

C Rodrigues red5_2 at hotmail.com
Sun Mar 18 13:47:21 EDT 2007

Type synonyms aren't applied as I would expect during kind checking.  What's 
going on here?

type WithList a b = b [a]
type FooPair a b = (b, a -> b)

-- error: `WithList' is applied to too many type arguments
ints1 :: WithList Int FooPair [Int]
ints1 = ([1], id)

-- error: `FooPair' is not applied to enough type arguments
ints2 :: (WithList Int FooPair) [Int]
ints2 = ([1], id)

-- after manually applying the first type synonym
ints3 :: FooPair [Int] [Int]
ints3 = ([1], id)

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