[GHC] #8809: Prettier error messages?

[GHC]

#8809: Prettier error messages?
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        Reporter:  joelteon          |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.9
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
  #8809,#10073,#10179                |
       Wiki Page:                    |
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Comment (by Rufflewind):

 I'd like to make an incremental attempt towards improving the aesthetics.
 Specifically, I wish to:

   - Add colors in a style similar to Clang/GCC.
   - Allow the color to be turned on and off via `-fdiagnostics-
 color=(always|auto|no)`.
   - Implement auto detection of color support (`auto`).
   - Display one line of code extracted from the original source code,
 along with a marker indicating the location of the error.

 So the final result should look like this, but with the usual white-on-
 black terminal colors:

 {{{
 #!html
 <code><pre><span style="font-weight: bold">/home/rf/revad.hs:26:1: <span
 style="color: magenta">warning:</span> [<span style="color: magenta
 ">-Wunused-top-binds</span>]
     Defined but not used: ‘</span>add<span style="font-weight:
 bold">’</span>
 add = Func $ \ (x, y) ->
 <span style="color: green; font-weight: bold">^~~</span>
 </pre></code>
 }}}

 Here is an attempt at implementing the first two objectives:
 https://github.com/ghc/ghc/compare/master...Rufflewind:diagnostics-color

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8809#comment:23>
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