[GHC] #15646: ghci takes super long time to find the type of large fractional number

[GHC]

#15646: ghci takes super long time to find the type of large fractional number
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        Reporter:  Johannkokos       |                Owner:
                                     |  JulianLeviston
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  GHCi              |              Version:  8.4.3
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #5692             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mpickering):

 Julian, can you please paste the exact error you are experiencing as I
 don't see how `Problem 1` can arise.

 When we bootstrap GHC, we first compile stage1 with stage0. So no problems
 here as the call to lookup `mkRational` is made when
 stage1 is run. When we build stage2, we first build prelude with stage1,
 including `GHC.Real` so there might be some problems here if a module
 needs to call `mkRational` before `GHC.Real` is compiled but this is hard
 to debug without any error messages or other information to be going from!

 I think at this point it would be very useful if you put your code up as a
 MR so that people can comment directly about what needs doing.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15646#comment:70>
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