[GHC] #10158: Panic compiling singletons: StgCmmEnv: variable not found

[GHC]

#10158: Panic compiling singletons: StgCmmEnv: variable not found
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        Reporter:  trommler          |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.11
  (CodeGen)                          |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  Compile-time      |               Test Case:
  crash                              |                Blocking:
      Blocked By:                    |  Differential Revisions:
 Related Tickets:                    |
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Comment (by simonpj):

 I nailed this one.  This diff fixes it.  It was a missing 'runFlatten'.
 However I propose not to commit a fix, because Richard's D653 refactors
 all that code and, I'm 99% certain, fixes the bug in a better way.

 I would like D653 to land though.  Richard is planning to do that on
 Monday

 Simon
 {{{
         Modified compiler/typecheck/TcInteract.hs
 diff --git a/compiler/typecheck/TcInteract.hs
 b/compiler/typecheck/TcInteract.hs
 index e83709c..4d4b31c 100644
 --- a/compiler/typecheck/TcInteract.hs
 +++ b/compiler/typecheck/TcInteract.hs
 @@ -1420,6 +1420,7 @@ shortCutReduction old_ev fsk ax_co fam_tc tc_args
    | otherwise
    = ASSERT( not (isDerived old_ev) )   -- Caller ensures this
      ASSERT( ctEvEqRel old_ev == NomEq )
 +    runFlatten $
      do { (xis, cos) <- flattenManyNom old_ev tc_args
                 -- ax_co :: F args ~ G tc_args
                 -- cos   :: xis ~ tc_args
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10158#comment:3>
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