[GHC] #14683: Hole-y partial type signatures lead to slow compile times

[GHC]

#14683: Hole-y partial type signatures lead to slow compile times
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        Reporter:  harpocrates       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by harpocrates):

 I've distilled the repo down to a single file. In the process, I've
 realized that the problem is actually not related to
 `PartialTypeSignatures`! On my machine:

 {{{
 $ time ghc-7.10.3 Grammar.hs
 17.71s user 1.30s system 97% cpu 19.543 total

 $ time ghc-8.0.2 Grammar.hs
 139.23s user 1.77s system 99% cpu 2:22.31 total

 $ time ghc-8.2.2 Grammar.hs
 127.42s user 1.53s system 98% cpu 2:11.08 total

 $ time ghc-head Grammar.hs
 130.42s user 1.06s system 99% cpu 2:12.58 total

 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14683#comment:3>
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