Ill formatted warning about tabulators

GHC-8.2.0.20170505 does not format warnings about tabulators very well. It seems to use the tab character for formatting, which yields too few spaces when formatted, and in turn too many characters are colored. (It is hard to present the problem in this ticket, though.)

$ cat Tabulator.hs
module Tabulator where

x :: Int
x =
        1*2*3*4*5*6*7*8*9
-- we use a tab for indentation here

$ ghc-8.2.0.20170505 -Wall Tabulator.hs 
[1 of 1] Compiling Tabulator        ( Tabulator.hs, Tabulator.o )

Tabulator.hs:5:1: warning: [-Wtabs]
    Tab character found here.
    Please use spaces instead.
  |
5 |     1*2*3*4*5*6*7*8*9
  | ^^^^^^^^

Trac metadata

Trac field	Value
Version	8.2.1-rc1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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