T11010.hs:9:34: error:
    • Couldn't match type ‘a1’ with ‘Int’
      Expected: a -> b
        Actual: a1 -> b
      ‘a1’ is a rigid type variable bound by
        a pattern with constructor:
          Fun :: forall a b. String -> (a -> b) -> Expr a -> Expr b,
        in a pattern synonym declaration
        at T11010.hs:9:26-36
    • In the declaration for pattern synonym ‘IntFun’
    • Relevant bindings include
        x :: Expr a1 (bound at T11010.hs:9:36)
        f :: a1 -> b (bound at T11010.hs:9:34)
  |
9 | pattern IntFun str f x = Fun str f x
  |                                  ^