[GHC] #11158: Combine exprIsTrivial and cpe_ExprIsTrivial

[GHC]

#11158: Combine exprIsTrivial and cpe_ExprIsTrivial
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        Reporter:  simonpj           |                Owner:
            Type:  task              |               Status:  patch
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1656
       Wiki Page:                    |
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Comment (by simonpj):

 It would be really really good to know why the tiny difference between the
 functions causes a seg fault.  Why doesn't Core Lint (on the output of
 `CorePrep`) catch the seg-fault?

 How to find it? Since the failing tests use the GHC API, that suggests
 that the code for GHC itself gets messed up, which is a pain -- GHC is a
 very big test-case!

 One idea: spit out a `pprTrace` whenever `cpe_exprIsTrivial` does
 something different to what `exprIsTrivial` would have.  I bet it doesn't
 happen much.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11158#comment:11>
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