[GHC] #12483: Improve parse error message on indentation mistake

[GHC]

#12483: Improve parse error message on indentation mistake
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        Reporter:  harendra          |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by bgamari):

 * failure:  Other => Incorrect warning at compile-time
 * type:  bug => feature request


Comment:

 Indeed these are frustratingly poor errors. I remember encountering this
 exact thing when I was learning the language.

 Improving this would require that someone take some time to think about
 how you can robustly catch this issue in the parser without introducing
 too much complexity.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12483#comment:1>
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