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

[GHC]

#12522: GHC 8.0.1 hangs, looping forever in type-checker
-------------------------------------+-------------------------------------
        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:                    |
-------------------------------------+-------------------------------------

Comment (by clinton):

 Oh yes, silly me. As you said, replacing the class with:

 {{{
 f :: TF (x, a) -> ()
 f _ = ()
 }}}

 also illustrates the bug. This still causes the compiler to loop forever
 in GHC HEAD 21st September 2016 (8.1.20160921)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12522#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler