[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 deech):

 Replying to [comment:14 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.

 I should have closed that issue, the [master
 branch](https://github.com/deech/fltkhs) and the latest [stable
 release](https://hackage.haskell.org/package/fltkhs)
 [should](https://github.com/deech/fltkhs/blob/master/Setup.hs#L47) work
 with Cabal 2.0.0.2 and GHC 8.2.1.

 I'm happy to help you through it.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12506#comment:15>
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