[GHC] #14769: The RecompBecause [TH] check is not resume-build-safe

[GHC]

#14769: The RecompBecause [TH] check is not resume-build-safe
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        Reporter:  nh2               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #481              |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 > I'd argue that removing the possibility to access an unsafePerformIO-
 based number generator at all would be an even stronger guarantee that
 non-determinism cannot be introduced, is that not accurate?

 Certainly, but there is a reason we use uniques: they allow very cheap
 comparison. Recovering this in a language with no sense of identity of
 pure values is not easy and I don't believe we are willing to eat the
 compile time regressions that would likely come from dropping uniques from
 the compiler.

 Of course, if you can show a rework of a subset of the compiler that
 doesn't regress in performance while avoiding a unique source, we would be
 quite interested.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14769#comment:12>
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