[GHC] #3401: unintuitive error message about unbalanced parentheses

[GHC]

#3401: unintuitive error message about unbalanced parentheses
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 Reporter:  tinlyx    |          Owner:                  
     Type:  bug       |         Status:  new             
 Priority:  normal    |      Milestone:                  
Component:  Compiler  |        Version:  6.10.3          
 Severity:  normal    |     Resolution:                  
 Keywords:            |       Testcase:                  
       Os:  Windows   |   Architecture:  Unknown/Multiple
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Comment (by isaacdupree):

 I'm not such a GHC author, but it's because the closing-parenthesis
 terminates the "do" layout (which is a non-error in some cases if there
 had been an open-parenthesis before the "do" for example).  I guess it
 reports the error in "do"-syntax before getting to the mismatched
 parenthesis error.

 That said, I'd think that GHC ought to be able to look ahead more.  Also
 for the "mismatched parentheses (maybe incorrect indentation?)" error.  If
 parentheses, *regardless* of layout, are still mismatched, then that's
 definitely an error that could be reported as such :-)

 (implementing that might be more adifficult though.)

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3401#comment:1>
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