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

[GHC]

#9723: Give Tab warning only once per file
-------------------------------------+-------------------------------------
       Reporter:  nomeata            |                   Owner:
           Type:  feature request    |                  Status:  new
       Priority:  low                |               Milestone:
      Component:  Compiler           |                 Version:  7.9
       Keywords:                     |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Unknown            |         Type of failure:
     Blocked By:                     |  None/Unknown
Related Tickets:                     |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:
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 Currently, when compiling a tabbed file, GHC spits out a huge number of
 warnings:

 {{{
 Main.hs:1:1: Warning: Tab character

 [..]

 Main.hs:89:1: Warning: Tab character

 Main.hs:90:1: Warning: Tab character

 Main.hs:91:1: Warning: Tab character

 Main.hs:92:1: Warning: Tab character

 Main.hs:99:4: Warning: Tab character

 Main.hs:100:4: Warning: Tab character

 Main.hs:101:4: Warning: Tab character
 }}}

 This is annoying and not very nice to our users.

 I suggest to replace it by
 {{{
 This file contains tabs (e.g. line n column m); please use spaces instead
 }}}
 or (to be nice to tools that parse this output)
 {{{
 Main.hs:1:1: Tab found here, and in n further locations. Please use spaces
 instead.
 }}}

 (This is clearly a low priority request, but also possibly some low-
 hanging fruit for new contributors.)

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