[GHC] #15002: Panic: collectNBinders

[GHC]

#15002: Panic: collectNBinders
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        Reporter:  crockeea          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.4.2
       Component:  Profiling         |              Version:  8.4.1
      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 nomeata):

 Thanks for the bisecting and minimization! Exemplary bug reporting!

 Judging from the report and the fact that profiling is necessary, it looks
 like profiling breaks the invariant that a joint point has `Lam`s as their
 right-hand-side. This can be confirmed by extending the `pprPanic` in
 `collectNBinders` to also show `orig_expr`. It might just be a case of
 looking through `Tick`s … but I am no expert on how profiled GHC is
 supposed to be handled.

 I am building the current `master` to look into it, but I don’t expect the
 build to finish in time to actually do that today. Unless someone beats me
 to it, I’ll have a lock tomorrow.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15002#comment:4>
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