[GHC] #7323: decoding GADTs gives internal error: stg_ap_v_ret

[GHC]

#7323: decoding GADTs gives internal error: stg_ap_v_ret
----------------------------+-----------------------------------------------
  Reporter:  heisenbug      |          Owner:                
      Type:  bug            |         Status:  closed        
  Priority:  normal         |      Milestone:  7.8.1         
 Component:  Compiler       |        Version:  7.7           
Resolution:  invalid        |       Keywords:                
        Os:  Linux          |   Architecture:  x86_64 (amd64)
   Failure:  Runtime crash  |     Difficulty:  Unknown       
  Testcase:  yes            |      Blockedby:                
  Blocking:                 |        Related:                
----------------------------+-----------------------------------------------

Comment(by int-e):

 Interestingly, ghc 7.4.1 used to produce a {{{runTimeError "Impossible
 case alternative"}}} for such cases rather than relying on the given value
 to be bottom. Is this the result of an optimization (getting rid of
 unreachable default branches in case, say) or an actual regression?

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7323#comment:7>
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