[GHC] #10817: Looping default associated type family without UndecidableInstances

[GHC]

#10817: Looping default associated type family without UndecidableInstances
-------------------------------------+-------------------------------------
        Reporter:  goldfire          |                Owner:
            Type:  bug               |               Status:  merge
        Priority:  normal            |            Milestone:  7.10.3
       Component:  Compiler (Type    |              Version:  7.10.2
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:  indexed-
                                     |  types/should_fail/T10817
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1262
-------------------------------------+-------------------------------------

Comment (by bgamari):

 goldfire, do you suppose you could backport this to `ghc-7.10`? I tried
 but there have been just enough differences in this area that I'm not sure
 I trust myself to get this right. Alternatively we could just punt. Your
 call.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10817#comment:6>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler