[GHC] #9392: "\n" is displayed weirdly in error messages

1 Aug 2014

      #9392: "\n" is displayed weirdly in error messages
-------------------------------------+-------------------------------------
       Reporter:  Artyom.Kazak       |                   Owner:
           Type:  bug                |                  Status:  new
       Priority:  low                |               Milestone:
      Component:  Compiler           |                 Version:  7.8.3
       Keywords:                     |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Unknown            |         Type of failure:  Other
     Blocked By:                     |               Test Case:
Related Tickets:                     |                Blocking:
                                     |  Differential Revisions:
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 Observe:

 {{{
 Prelude> "a\nb" + ()

 <interactive>:2:10:
     Couldn't match expected type ‘[Char]’ with actual type ‘()’
     In the second argument of ‘(+)’, namely ‘()’
     In the expression:
       "a\n\
       \b"
       + ()
 }}}

 Moreover, if “\n” is at the end of the string, it simply gets eaten:

 {{{
 Prelude> "a\n" + ()

 <interactive>:3:9:
     Couldn't match expected type ‘[Char]’ with actual type ‘()’
     In the second argument of ‘(+)’, namely ‘()’
     In the expression: "a" + ()
 }}}

 It happens in GHC as well as GHCi. Tested on 7.8.3.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9392
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