>>749 の例に
instance VAFun a [Int] [Int] where
withVAList g = g []

createList :: VAFun Int [Int] x => x
createList = withVAList id
を加えてやるとInt型限定のcreateListができた。

createList (1::Int) (2::Int) (3::Int) :: [Int]
=> [1,2,3]