[GHC] #8946: Using hdevtools caused "Evaluated the place holder for a PostTcKind"

[GHC]

#8946: Using hdevtools caused "Evaluated the place holder for a PostTcKind"
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       Reporter:  tbelaire        |             Owner:
           Type:  bug             |            Status:  new
       Priority:  normal          |         Milestone:
      Component:  Compiler        |           Version:  7.8.1-rc1
       Keywords:                  |  Operating System:  MacOS X
   Architecture:  x86_64 (amd64)  |   Type of failure:  None/Unknown
     Difficulty:  Unknown         |         Test Case:
     Blocked By:                  |          Blocking:
Related Tickets:                  |
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 I was tying to get hdevtools to work, and cloned it and pulled in a bunch
 of the open pull requests.
 You can see the state it's in at github.com/tbelaire/hdevtools.

 {{{
 git clone git at github.com:tbelaire/hdevtools
 cd hdevtools
 cabal sandbox init
 cabal install
 cd ..
 }}}

 I could not reproduce the problem on a small test file, so I'm afraid I'll
 have to demonstrate it on my vinyl-json package.

 {{{
 git clone git at github.com:tbelaire/vinyl-json
 cd vinyl-json/
 cabal sandbox init
 cabal install
 hdevtools type src/Data/Vinyl/JSON.hs 42 15

 panic! (the 'impossible' happened)
   (GHC version 7.8.20140130 for x86_64-apple-darwin):
         Evaluated the place holder for a PostTcKind

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

 I also get hpc has closed due to a problem a lot when compiling things,
 but I think that's unrelated.  The dynamic lib seems to be gone.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8946>
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