[GHC] #5603: Impossible case alternative

[GHC]

#5603: Impossible case alternative
---------------------------------+------------------------------------------
    Reporter:  igloo             |        Owner:  simonpj     
        Type:  bug               |       Status:  new         
    Priority:  highest           |    Milestone:  7.4.1       
   Component:  Compiler          |      Version:  7.3         
    Keywords:                    |     Testcase:  T5603       
   Blockedby:                    |   Difficulty:              
          Os:  Unknown/Multiple  |     Blocking:              
Architecture:  Unknown/Multiple  |      Failure:  None/Unknown
---------------------------------+------------------------------------------

Comment(by simonpj@…):

 commit f96db3ca8a7c83cc3da242fad761fb05543068f6
 {{{
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Wed Nov 9 23:32:20 2011 +0000

     Establish the invariant that (LitAlt l) is always unlifted

     ...and make sure it is, esp in the call to findAlt in
     the mighty Simplifier.  Failing to check this led to
     searching a bunch of DataAlts for a LitAlt Integer.
     Naughty.  See Trac #5603 for a case in point.

  compiler/basicTypes/Literal.lhs    |    6 +++++-
  compiler/coreSyn/CoreLint.lhs      |   13 ++++++-------
  compiler/coreSyn/CoreSyn.lhs       |   30 +++++++++++++++++++++++++-----
  compiler/deSugar/DsUtils.lhs       |    8 +++++---
  compiler/prelude/PrelRules.lhs     |    3 +++
  compiler/simplCore/Simplify.lhs    |    2 ++
  compiler/specialise/SpecConstr.lhs |    4 +++-
  7 files changed, 49 insertions(+), 17 deletions(-)
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5603#comment:6>
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