[GHC] #12386: Infinite loop when showing type family error

[GHC]

#12386: Infinite loop when showing type family error
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        Reporter:  elliottt          |                Owner:  simonpj
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.0.2
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 This is a black-hole kind of bug.

 Works ok if you move `F` out of the type class
 {{{
 type family F a t :: *

 class C a where
   type family T a :: *
   type T a = F a
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12386#comment:4>
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