[GHC] #12506: Compile time regression in GHC 8.

[GHC]

#12506: Compile time regression in GHC 8.
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        Reporter:  deech             |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by tdammers):

 I tried reproducing the problem with GHC 8.2.1, but unfortunately the
 build instructions no longer work with Cabal 2.0.x. It seems that `fltkhs`
 doesn't support Cabal 2.0, and [this github
 issue](https://github.com/deech/fltkhs/issues/38) tells me this might not
 get fixed anytime soon.

 Is there an up-to-date way of reproducing the issue that I could use?
 Preferably one that doesn't involve `stack`, simply because I want to hook
 a custom-built GHC directly from git into the build so I can play with
 some things and cherry-pick selected changes, and this isn't trivial with
 stack.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12506#comment:14>
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