Missing warning on duplicate import

The following program does not give a warning:

{-# OPTIONS_GHC -Wall #-}
import Data.List
import Data.List

main :: IO ()
main = print $ sort "hello"

But this program does:

{-# OPTIONS_GHC -Wall #-}

import Data.List(sort)
import Data.List

main :: IO ()
main = print $ sort "hello"

with:

    Warning: Redundant import of: `sort'
             It is also imported from Data.List at Test.hs:4:0-15

It seems surprising that 100% identical imports aren't given as warnings, as in the first example.

Trac metadata

Trac field	Value
Version	6.10.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	ndmitchell@gmail.com
Operating system
Architecture