[GHC] #10849: Injective type families broke debug build

[GHC]

#10849: Injective type families broke debug build
-------------------------------------+-------------------------------------
              Reporter:  nomeata     |             Owner:  jstolarek
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.2
  (Type checker)                     |
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  GHC rejects
  Unknown/Multiple                   |  valid program
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
-------------------------------------+-------------------------------------
 Hi,

 since changeset:3744578 Travis observes these failures when built with
 DEBUG on:
 {{{
 Compile failed (status 256) errors were:
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 7.11.20150903 for x86_64-unknown-linux):
         ASSERT failed! file compiler/typecheck/TcInteract.hs, line 1381

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug


 *** unexpected failure for T5490(normal)

 Actual stderr output differs from expected:
 --- ./indexed-types/should_fail/T5439.stderr.normalised 2015-09-03
 04:54:51.184120403 +0000
 +++ ./indexed-types/should_fail/T5439.comp.stderr.normalised    2015-09-03
 04:54:51.184120403 +0000
 @@ -1,25 +1,5 @@
 +ghc: panic! (the 'impossible' happened)
 +  (GHC version 7.11.20150903 for x86_64-unknown-linux):
 +       ASSERT failed! file compiler/typecheck/TcInteract.hs, line 1381

 -T5439.hs:82:28:
 -    Couldn't match type ‘Attempt (HElemOf rs)’
 -                   with ‘Attempt (HHead (HDrop n0 l0)) -> Attempt
 (HElemOf l0)’
 -    Expected type: f (Attempt (HNth n0 l0) -> Attempt (HElemOf l0))
 -      Actual type: f (Attempt (WaitOpResult (WaitOps rs)))
 -    Relevant bindings include
 -      register :: Bool -> Peano n -> WaitOps (HDrop n rs) -> IO Bool
 -        (bound at T5439.hs:64:9)
 -      ev :: f (Attempt (WaitOpResult (WaitOps rs)))
 -        (bound at T5439.hs:61:22)
 -      ops :: WaitOps rs (bound at T5439.hs:61:18)
 -      registerWaitOp :: WaitOps rs
 -                        -> f (Attempt (WaitOpResult (WaitOps rs))) -> IO
 Bool
 -        (bound at T5439.hs:61:3)
 -    In the first argument of ‘complete’, namely ‘ev’
 -    In the expression: complete ev
 -
 -T5439.hs:82:39:
 -    Couldn't match expected type ‘Peano n0’
 -                with actual type ‘Attempt α0’
 -    In the second argument of ‘($)’, namely
 -      ‘Failure (e :: SomeException)’
 -    In the second argument of ‘($)’, namely
 -      ‘inj $ Failure (e :: SomeException)’
 \ No newline at end of file
 +Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 \ No newline at end of file
 *** unexpected failure for T5439(normal)
 }}}
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10849>
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