Demonstrate a bug in yesod-form's intField

IntFieldBug.hs

{-# LANGUAGE TypeFamilies, QuasiQuotes, MultiParamTypeClasses,
             TemplateHaskell, OverloadedStrings #-}

import Control.Applicative
import Data.Text
import Yesod
import Yesod.Form

data HelloWorld = HelloWorld

instance RenderMessage HelloWorld FormMessage where
    renderMessage _ _ = defaultFormMessage

mkYesod "HelloWorld" [parseRoutes|
/ FormR GET POST
|]

instance Yesod HelloWorld where
    approot _ = ""



data SomeFormData = SFD { field :: Int }
    deriving Show

dataForm :: Html -> MForm HelloWorld HelloWorld  (FormResult SomeFormData, Widget)
dataForm = renderDivs $ SFD
    <$> areq intField "Field" Nothing

largeInt :: Int
largeInt = maxBound

getFormR :: Handler RepHtml
getFormR = do
     ((_, widget), enctype) <- generateFormPost dataForm
     defaultLayout [whamlet|
<p> Enter a large Int value, e.g. on a 64bit system maxBound :: Int = #{largeInt}
<form method=post action=@{FormR} enctype=#{enctype}>
    ^{widget}
    <input type=submit>
|]

postFormR :: Handler RepHtml
postFormR = do
    ((result, widget), enctype) <- runFormPost dataForm
    case result of
      FormSuccess f -> defaultLayout [whamlet|Received #{field f}|]
      _ -> defaultLayout [whamlet|Something bad happened|]



main :: IO ()
main = warpDebug 3000 HelloWorld