Haskell 让do中的表达式导致错误

删除

let（！）=在
中翻转valFromObj并替换
tweet！“user”
使用
valFromObj“user”tweet
等，一切正常。
这是由引起的，这导致
（！）
的类型被推断为
JSObject JSValue->String->Result（JSObject JSValue）
，因为它在

[1 of 1] Compiling Main             ( twitter.hs, interpreted )

twitter.hs:11:27:
    Couldn't match expected type `[Char]'
                with actual type `JSObject JSValue'
    Expected type: String
      Actual type: JSObject JSValue
    In the `user' field of a record
    In the first argument of `return', namely
      `Status {user = user, text = text}'
Failed, modules loaded: none.

userObject结果状态
makeStatus tweet=do
用户对象结果a
（！）=flip valFromObj
这是由引起的，这导致
（！）
的类型被推断为
JSObject JSValue->String->Result（JSObject JSValue）
，因为它在

[1 of 1] Compiling Main             ( twitter.hs, interpreted )

twitter.hs:11:27:
    Couldn't match expected type `[Char]'
                with actual type `JSObject JSValue'
    Expected type: String
      Actual type: JSObject JSValue
    In the `user' field of a record
    In the first argument of `return', namely
      `Status {user = user, text = text}'
Failed, modules loaded: none.

userObject结果状态
makeStatus tweet=do
用户对象结果a
（！）=flip valFromObj

userObject <- tweet ! "user"

makeStatus :: JSObject JSValue -> Result Status
makeStatus tweet = do
    userObject <- tweet ! "user"
    user <- userObject ! "screen_name"
    text <- tweet ! "text"
    return Status {user = user, text = text}
  where
    (!) :: JSON a => JSObject JSValue -> String -> Result a
    (!) = flip valFromObj