[GHC] #12522: GHC 8.0.1 hangs, looping forever in type-checker

[GHC]

#12522: GHC 8.0.1 hangs, looping forever in type-checker
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        Reporter:  clinton           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by jstolarek):

 Surprising. I was expecting that GHC will hang on a black-hole but this
 indeed looks like an infinite loop in the type checker. I'm afraid Simon
 or Richard will have to take a look at this.

 Oh, and `f` need not be a part of a type class. It can be a standalone
 function with undefined definition.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12522#comment:2>
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