更改脚手架时输入']'上的错误解析错误

Question

我已经从脚手架模板创建了一个简单的yesod，并希望更改路径/的内容。

Yesod类型类的实例如下所示：

instance Yesod App where
    -- Controls the base of generated URLs. For more information on modifying,
    -- see: https://github.com/yesodweb/yesod/wiki/Overriding-approot
    approot :: Approot App
    approot = ApprootRequest $ \app req ->
        case appRoot $ appSettings app of
            Nothing -> getApprootText guessApproot app req
            Just root -> root

    -- Store session data on the client in encrypted cookies,
    -- default session idle timeout is 120 minutes
    makeSessionBackend :: App -> IO (Maybe SessionBackend)
    makeSessionBackend _ = Just <$> defaultClientSessionBackend
        120    -- timeout in minutes
        "config/client_session_key.aes"

    -- Yesod Middleware allows you to run code before and after each handler function.
    -- The defaultYesodMiddleware adds the response header "Vary: Accept, Accept-Language" and performs authorization checks.
    -- Some users may also want to add the defaultCsrfMiddleware, which:
    --   a) Sets a cookie with a CSRF token in it.
    --   b) Validates that incoming write requests include that token in either a header or POST parameter.
    -- To add it, chain it together with the defaultMiddleware: yesodMiddleware = defaultYesodMiddleware . defaultCsrfMiddleware
    -- For details, see the CSRF documentation in the Yesod.Core.Handler module of the yesod-core package.
    yesodMiddleware :: ToTypedContent res => Handler res -> Handler res
    yesodMiddleware = defaultYesodMiddleware

    isAuthorized
        :: Route App  -- ^ The route the user is visiting.
        -> Bool       -- ^ Whether or not this is a "write" request.
        -> Handler AuthResult
    -- Routes not requiring authenitcation.
    isAuthorized FaviconR _ = return Authorized
    isAuthorized RobotsR _ = return Authorized
    -- Default to Authorized for now.
    isAuthorized _ _ = return Authorized

    -- This function creates static content files in the static folder
    -- and names them based on a hash of their content. This allows
    -- expiration dates to be set far in the future without worry of
    -- users receiving stale content.
    addStaticContent
        :: Text  -- ^ The file extension
        -> Text -- ^ The MIME content type
        -> LByteString -- ^ The contents of the file
        -> Handler (Maybe (Either Text (Route App, [(Text, Text)])))
    addStaticContent ext mime content = do
        master <- getYesod
        let staticDir = appStaticDir $ appSettings master
        addStaticContentExternal
            minifym
            genFileName
            staticDir
            (StaticR . flip StaticRoute [])
            ext
            mime
            content
      where
        -- Generate a unique filename based on the content itself
        genFileName lbs = "autogen-" ++ base64md5 lbs

    -- What messages should be logged. The following includes all messages when
    -- in development, and warnings and errors in production.
    shouldLogIO :: App -> LogSource -> LogLevel -> IO Bool
    shouldLogIO app _source level =
        return $
        appShouldLogAll (appSettings app)
            || level == LevelWarn
            || level == LevelError

    makeLogger :: App -> IO Logger
    makeLogger = return . appLogger  

我从上面的defaultLayout实例中删除了Yesod方法，根路径的处理程序如下所示：

{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilies #-}
module Handler.Home where

import Import
import Yesod.Form.Bootstrap3 (BootstrapFormLayout (..), renderBootstrap3)
import Text.Julius (RawJS (..))


-- This is a handler function for the GET request method on the HomeR
-- resource pattern. All of your resource patterns are defined in
-- config/routes
--
-- The majority of the code you will write in Yesod lives in these handler
-- functions. You can spread them across multiple files if you are so
-- inclined, or create a single monolithic file.
getHomeR :: Handler Html
getHomeR = defaultLayout [whamlet|<h2>Previously submitted files|]

当我尝试构建时，它说：

/home/developer/haskell/yeplay/src/Handler/Home.hs:21:48: error: parse error on input ‘]’
   |
21 | getHomeR = defaultLayout [whamlet|Hello World!|]
   |            

我究竟做错了什么？

Answer 1

您可以将{-# LANGUAGE QuasiQuotes #-}添加到您的语言扩展名中。

getHomeR = defaultLayout [whamlet|Hello World!|]

在上面的陈述中，whamlet来自准引用者，它将哈姆雷特语法转换为Widget。因此，要启用whamlet，您必须添加QuasiQuotes。