[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:  13122
 Related Tickets:                    |  Differential Rev(s):
  #8809,#10073,#10179,#12906         |
       Wiki Page:                    |
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Comment (by mpickering):

 Phil makes a good point about where the semantic information should be
 embedded. In fact, this semantic information is already there in two
 cases, which flag the warning was caused by and the position of the error
 (see `TcRnMonad.add_warn_at`). In fact, looking at `ErrMsg`, there is
 already a lot of semantic information present there as well. These errors
 are then caught by `ioMsgMaybe` in `HscMain` and reported by `throwErrors`
 where the information is somehow lost but I have to go!

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8809#comment:54>
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