[GHC] #6068: Panic in GHCi when using functional dependencies and promoted kinds

[GHC]

#6068: Panic in GHCi when using functional dependencies and promoted kinds
-------------------------------------+------------------------------------
        Reporter:  goldfire          |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  GHCi              |          Version:  7.5
      Resolution:                    |         Keywords:  PolyKinds
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  GHCi crash        |       Difficulty:  Unknown
       Test Case:  polykinds/T6068   |       Blocked By:
        Blocking:                    |  Related Tickets:
-------------------------------------+------------------------------------
Changes (by nomeata):

 * cc: hvr (added)
 * status:  closed => new
 * resolution:  fixed =>


Comment:

 In a fresh checkout (95216e8fa0ecb98189dce29f0b89b3b0f8d439c6,
 `distclean`’ed and built), I get:

 {{{
 =====> T6068(ghci) 2026 of 3814 [0, 0, 0]
 cd ./polykinds && HC='/home/jojo/build/haskell/ghc/inplace/bin/ghc-stage2'
 HC_OPTS='-dcore-lint -dcmm-lint -dno-debug-output -no-user-package-db
 -rtsopts -fno-ghci-history ' '/home/jojo/build/haskell/ghc/inplace/bin
 /ghc-stage2' --interactive -v0 -ignore-dot-ghci -dcore-lint -dcmm-lint
 -dno-debug-output -no-user-package-db -rtsopts -fno-ghci-history
 <T6068.script >T6068.run.stdout 2>T6068.run.stderr
 Actual stderr output differs from expected:
 --- /dev/null   2013-11-12 10:20:30.826690103 +0100
 +++ ./polykinds/T6068.run.stderr        2013-11-12 10:39:54.333361005
 +0100
 @@ -0,0 +1,9 @@
 +ghc-stage2: panic! (the 'impossible' happened)
 +  (GHC version 7.7.20131108 for x86_64-unknown-linux):
 +       ASSERT failed!
 +    file compiler/typecheck/TcMType.lhs line 809
 +    [D] _ :: mp{tv aEn} [tau[0]]
 +             ghc-prim:GHC.Types.~{(w) tc 31Q} kp_aEi{tv} [tau[0]]
 (CIrredEvCan)
 +
 +Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 +
 Actual stdout output differs from expected:
 --- ./polykinds/T6068.stdout    2013-10-05 15:18:57.118579683 +0200
 +++ ./polykinds/T6068.run.stdout        2013-11-12 10:39:54.193361010
 +0100
 @@ -1 +0,0 @@
 -exists Nothing :: Floop a mp => Existential mp
 *** unexpected failure for T6068(ghci)
 }}}

 Strangely, on [https://s3.amazonaws.com/archive.travis-
 ci.org/jobs/13835382/log.txt travis] it succeeded.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6068#comment:3>
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