[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 dalaing):

 I was a bit torn as well.  I mostly liked the idea of picking some low
 hanging fruit to get into GHC hacking :)

 I like using the go-to-previous-error and go-to-next-error features in my
 editor, and if a few tabs have crept in it'd be nice to just fix them up
 in my usual cycle.

 On the other hand, most of the tabs I've come across in the checkout of
 GHC have been in files where tabs are used consistently throughout the
 file (time, xhtml, ...) - in which case I'd prefer one warning after which
 I'd get my editor to retab the file and move on.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9723#comment:7>
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