[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:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by JulianLeviston):

 Chatted a bit more with osa1 about this now on IRC. Seems TH has the same
 issue(s), because the use-sites for `mkFractionalLit` includes the
 `cvtOverLit :: Lit -> CvtM (HsOverLit GhcPs)` function from
 hsSync/Convert.hs... the `cvtOverLit (RationalL r)` clause, which reads:

 ```
 cvtOverLit (RationalL r)
   = do { force r; return $ mkHsFractional (mkFractionalLit r) }

 ```

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15646#comment:27>
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