[GHC] #12234: 'deriving Eq' on recursive datatype makes ghc eat a lot of CPU and RAM

[GHC]

#12234: 'deriving Eq' on recursive datatype makes ghc eat a lot of CPU and RAM
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        Reporter:  slyfox            |                Owner:
            Type:  bug               |               Status:  merge
        Priority:  normal            |            Milestone:  8.0.3
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  deriving-perf
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Compile-time      |            Test Case:
  performance bug                    |  perf/should_compile/T12234
      Blocked By:                    |             Blocking:
 Related Tickets:  #13056            |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by RyanGlScott):

 * related:   => #13056


Comment:

 #13056 demonstrates another occurrence of this bug, this time involving
 `Foldable`. But unlike the program in this ticket, it doesn't require any
 GHC extensions like `UndecidableInstances` to trigger it.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12234#comment:14>
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