[GHC] #5439: Crash in TcEnv.lhs line 461

[GHC]

#5439: Crash in TcEnv.lhs line 461
---------------------------------+------------------------------------------
  Reporter:  mikhail.vorozhtsov  |          Owner:                  
      Type:  bug                 |         Status:  new             
  Priority:  normal              |      Milestone:                  
 Component:  Compiler            |        Version:  7.3             
Resolution:                      |       Keywords:                  
  Testcase:                      |      Blockedby:                  
Difficulty:                      |             Os:  Unknown/Multiple
  Blocking:                      |   Architecture:  Unknown/Multiple
   Failure:  Compile-time crash  |  
---------------------------------+------------------------------------------
Changes (by mikhail.vorozhtsov):

  * status:  closed => new
  * resolution:  fixed =>


Comment:

 I'm still getting the panic on my file.
 {{{
 $ git log -n 3 --format=oneline
 fa71e6c795489ec267e0d048395c2c52bea6a164 Fix #4988: we were wrongly
 running exception h...
 c27df60d69ad54a69723510c57e238f31a59c532 Two small further extensions to
 associated typ...
 eb46e0de6eab60483f38ed2088d9de13d8e74e2f Fix the trimming of bind_fvs
 (fixes Trac #5439...
 $ ./validate --slow
 ...
 $ grep panic testlog
 $ ./inplace/bin/ghc-stage1 -c -fforce-recomp ~/Bug.hs

 /home/mikhail_vorozhtsov/Bug.hs:83:39:
     Couldn't match expected type `Peano n0'
                 with actual type `Attempt α0'
     In the return type of a call of `Failure'
     In the second argument of `($)', namely
       `Failure (e :: SomeException)'
     In the second argument of `($)', namely
       `inj $ Failure (e :: SomeException)'
 }}}
 So far so good (the type error is expected), but then:
 {{{
 ./inplace/bin/ghc-stage2 -c -fforce-recomp ~/Bug.hs
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 7.3.20110901 for x86_64-unknown-linux):
         ASSERT failed! file compiler/typecheck/TcEnv.lhs line 461
 register{v amR} [lid]
 forall n{tv amS} [tv].
 main:Main.HDropClass{tc r1d} n{tv amS} [tv] rs{tv amO} [ssk] =>
 ghc-prim:GHC.Types.Bool{(w) tc 3c}
 -> main:Main.Peano{tc rx} n{tv amS} [tv]
 -> main:Main.WaitOps{tc rr}
      (main:Main.HDrop{tc r1c} n{tv amS} [tv] rs{tv amO} [ssk])
 -> ghc-prim:GHC.Types.IO{tc 32I} ghc-prim:GHC.Types.Bool{(w) tc 3c}

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}
 If I fix the type error reported by the stage1 compiler (by replacing "$
 inj $" with "$ inj n $"), the panic goes away. The bootstrap compiler is
 GHC 7.0.3.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5439#comment:4>
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