haskell gogol - 已安装的应用程序凭据示例 : Couldn't match kind ‘[Symbol]’ with ‘*’

Question

我正在尝试 installed application credentials 的例子
在 gogol package .

这是示例(刚刚从已安装的应用程序凭据页面复制):

{-# LANGUAGE ScopedTypeVariables #-}
import Data.Proxy     (Proxy (..))
import Data.Text      as T
import Data.Text.IO   as T
import System.Exit    (exitFailure)
import System.Info    (os)
import System.Process (rawSystem)
redirectPrompt :: AllowScopes (s :: [Symbol]) => OAuthClient -> proxy s -> IO (OAuthCode s)
redirectPrompt c p = do
    let url = formURL c p
    T.putStrLn $ "Opening URL " `T.append` url
    _ <- case os of
        "darwin" -> rawSystem "open"     [unpack url]
        "linux"  -> rawSystem "xdg-open" [unpack url]
    _        -> T.putStrLn "Unsupported OS" >> exitFailure
    T.putStrLn "Please input the authorisation code: "
    OAuthCode <$> T.getLine

当我编译代码时，出现如下错误:

Illegal kind signature: ‘s’
  Perhaps you intended to use KindSignatures
In the type signature for ‘redirectPrompt’

Illegal kind: ‘[Symbol]’ Perhaps you intended to use DataKinds

所以我在我的代码中添加了这两行:

{-# LANGUAGE KindSignatures    #-}
{-# LANGUAGE DataKinds         #-} 

然后，再次编译。它显示以下错误消息:

• Couldn't match kind ‘[Symbol]’ with ‘*’
  When matching the kind of ‘proxy’
• In the second argument of ‘formURL’, namely ‘p’
  In the expression: formURL c p
  In an equation for ‘url’: url = formURL c p
• Relevant bindings include
    p :: proxy s (bound at app/Main.hs:36:18)
    redirectPrompt :: OAuthClient -> proxy s -> IO (OAuthCode s)
      (bound at app/Main.hs:36:1)

我不知道为什么会出错.. p的类型看起来和 formURL 一样需要一个。

-- https://hackage.haskell.org/package/gogol-0.1.1/docs/Network-Google-Auth.html#v:formURL
formURL :: AllowScopes (s :: [Symbol]) => OAuthClient -> proxy s -> Text

我误解了什么吗？

更新

我使用的版本是 lts-7.19。
从 lts-7.19 更改为 lts-8.0 后，它起作用了。

lts-7.19 的 ghc 版本是 8.0.1。
lts-8.0 是 8.0.2。
以下是 ghc-8.0.2-released 的一些笔记.

Answer 1

与 lts-8.0 一起使用以及 .cabal 中的正确依赖项

 build-depends:    base
                 , gogol
                 , gogol-core
                 , process
                 , text

您需要 {-# LANGUAGE OverloadedStrings #-}和 import GHC.TypeLits哪里 Symbol被定义为。

{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE KindSignatures    #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE DataKinds         #-}

module Main where

import Network.Google.Auth
import GHC.TypeLits

import Data.Proxy     (Proxy (..))
import Data.Text      as T
import Data.Text.IO   as T
import System.Exit    (exitFailure)
import System.Info    (os)
import System.Process (rawSystem)

redirectPrompt :: AllowScopes (s :: [Symbol]) => OAuthClient -> proxy s -> IO (OAuthCode s)
redirectPrompt c p = do
 let url = formURL c p
 T.putStrLn $ "Opening URL " `T.append` url
  _ <- case os of
        "darwin" -> rawSystem "open"     [unpack url]
        "linux"  -> rawSystem "xdg-open" [unpack url]
        _        -> T.putStrLn "Unsupported OS" >> exitFailure
T.putStrLn "Please input the authorisation code: "
OAuthCode <$> T.getLine 

main = print "working"