是否可以显示应用 Haskell 类型族函数的结果？

Question

例如，如果我有这些奇怪的类型：

{-# LANGUAGE TypeFamilies #-}
type family WeirdFamily a
type instance WeirdFamily () = Int
type instance WeirdFamily (a, b) = (a, WeirdFamily b)

我可以WeirdFamily (Bool, (Char, ()))通过键入以下内容来显示（例如在 GHCi 中）结果：

:t WeirdFamily (Bool, (Char, ()))

到 GHCi？

Answer 1

使用kind!.

:kind! WeirdFamily (Bool, (Char, ()))
WeirdFamily (Bool, (Char, ())) :: *
= (Bool, (Char, Int))