[GHC] #14173: GHC hangs during type-checking

[GHC]

#14173: GHC hangs during type-checking
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        Reporter:  lightandlight     |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 With 8.2.1 this fails with,
 {{{
 hi.hs:5:19: error:
     • Reduction stack overflow; size = 201
       When simplifying the following type: g ~ Compose f'0 g'0
       Use -freduction-depth=0 to disable this check
       (any upper bound you could choose might fail unpredictably with
        minor updates to GHC, so disabling the check is recommended if
        you're sure that type checking should terminate)
     • In the expression: _Wrapping Compose . traverse
       In an equation for ‘traverseCompose’:
           traverseCompose = _Wrapping Compose . traverse
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14173#comment:2>
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