[GHC] #13233: typePrimRep panic while compiling GHC with profiling

[GHC]

#13233: typePrimRep panic while compiling GHC with profiling
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonmar):

 Replying to [comment:21 simonpj]:
 > I strongly agree that we should write down the invariants for ticks

 So just to write down what we discussed the other day:

 * I believe there are (or were) no invariants on where ticks can appear in
 Core.  However, there's an invariant that `(#,#)` must be directly applied
 to its type arguments, with no intervening ticks. (maybe it's more general
 than this?).  Core Lint should really check this invariant.
 * We think that this invariant is satisfied by the desugarer but gets
 violated when the simplifier moves ticks inside type applications
 (https://phabricator.haskell.org/diffusion/GHC/browse/master/compiler/coreSyn/CoreUtils.hs;639e702b6129f501c539b158b982ed8489e3d09c$342-344).
 We don't know if there are other places that might violate the invariant.
 * I (@simonmar) was worried that if we just stop doing this we might lose
 other beneficial transformations.  @bgamari is going to try it and check.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13233#comment:23>
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