模块Language.Haskell.Generate.Expression失败

Question

https://github.com/bennofs/haskell-generate

module Language.Haskell.Generate.Expression 
  ( Expression(..)
  , app
  ) where

import Language.Haskell.Exts.Syntax

newtype Expression t = Expression { runExpression :: Exp }

app :: Expression (a -> b) -> Expression a -> Expression b
app (Expression a) (Expression b) = Expression $ App a b


/workspace/haskell/haskell-generate/src/Language/Haskell/Generate/Expression.hs:8:54:
Expecting one more argument to ‘Exp’
Expected a type, but ‘Exp’ has kind ‘* -> *’
In the type ‘Exp’
In the definition of data constructor ‘Expression’
In the newtype declaration for ‘Expression’

失败，模块加载：无。

任何想法？