[GHC] #2431: allow empty case analysis

[GHC]

#2431: allow empty case analysis
---------------------------------+------------------------------------------
 Reporter:  RalfHinze            |          Owner:         
     Type:  feature request      |         Status:  new    
 Priority:  low                  |      Milestone:  _|_    
Component:  Compiler             |        Version:  6.8.3  
 Severity:  minor                |     Resolution:         
 Keywords:  empty case analysis  |     Difficulty:  Unknown
 Testcase:                       |   Architecture:  Unknown
       Os:  Unknown              |  
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Comment (by simonmar):

 Replying to [comment:6 malcolm.wallace at cs.york.ac.uk]:
 > I tried to think of how parsing might go wrong.  Consider the following
 (contrived) example:
 >
 > {{{
 > case foo of
 >   [] ->
 >     case bar of
 >   (x:xs) ->
 >     baz
 > }}}
 >
 > Did you spot that the second alternative is indented with a tab rather
 than spaces, (with editor tab width set to 2 instead of 8)?

 I realise the example is contrived, but I don't think we need to consider
 it.  The Haskell report defines tab stops to be 8 characters apart, so you
 should always have your editor set to use 8-character tab stops when
 editing Haskell code, because that's how the compiler sees it.  Anything
 else will cause confusion, in many more ways than just the example above.
 If you don't like 8-char tabs then fine: use spaces instead, and `-fwarn-
 tabs`, but you should still set your editor to use 8-char tabs so that you
 can read other people's code.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2431#comment:7>
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