[GHC] #11276: GHC hangs/takes an exponential amount of time with simple program

[GHC]

#11276: GHC hangs/takes an exponential amount of time with simple program
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        Reporter:  mpickering        |                Owner:  gkaracha
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.10.3
      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 Ben Gamari <ben@…>):

 In [changeset:"0acdcf2482d24903b504e6b34fa745ef855ff00d/ghc"
 0acdcf24/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="0acdcf2482d24903b504e6b34fa745ef855ff00d"
 Avoid generating guards for CoPats if possible (Addresses #11276)

 When translating a `CoPat` to `PmPat` check whether the wrapper
 is just a hole or a cast with refl. In these cases we can safely
 drop the wrapper and generate less guard patterns. Fixes T11276.

 Test Plan: validate

 Reviewers: bgamari, austin

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1729

 GHC Trac Issues: #11276
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11276#comment:10>
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