[GHC] #9723: Give Tab warning only once per file

[GHC]

#9723: Give Tab warning only once per file
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        Reporter:  nomeata           |                   Owner:  dalaing
            Type:  feature request   |                  Status:  patch
        Priority:  low               |               Milestone:
       Component:  Compiler          |                 Version:  7.9
      Resolution:                    |                Keywords:  newcomer
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:  Phab:D760
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Comment (by nomeata):

 > So tooling can't highlight all offending lines at once, and would need
 to be made aware that this warning actually affects more lines.

 This is a good thing. If you edit a file with tabs in every line,
 highlighting every line is more annoying than helpful, IMHO.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9723#comment:6>
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