RequestBody被應用到太多的類型參數

Question

什麼不下列函數不進行類型檢查：

import qualified Control.Exception as E 
import Data.Conduit (ResourceT) 
import Network.HTTP.Types (Method, Status(..)) 
import Network.HTTP.Conduit 
import qualified Data.ByteString.Lazy.Char8 as LBS 

doHttps :: Method -> String 
     -> Maybe (RequestBody (ResourceT IO)) 
     -> IO (Either E.SomeException (Response LBS.ByteString)) 
doHttps reqMethod url body = undefined 

它產生以下錯誤：

RequestBody is applied to too many type arguments 
    In the type signature for `doHttps': 
     doHttps :: Method 
       -> String 
        -> Maybe (RequestBody (ResourceT IO)) 
         -> IO (Either E.SomeException (Response LBS.ByteString)) 
Failed, modules loaded: none. 

的doHttps函數是一個簡化版本this function。但顯然，在模塊typechecks原來的功能，但上面的代碼片段不起作用。爲什麼會發生？

Answer 1

不同版本的http-conduit庫。在版本1 *，RequestBody了一個類型參數：

http://hackage.haskell.org/package/http-conduit-1.9.6/docs/Network-HTTP-Conduit.html#t:RequestBody

然而，在版本2 *，它並不需要一個類型參數：

http://hackage.haskell.org/package/http-conduit-2.0.0/docs/Network-HTTP-Conduit.html#t:RequestBody