[GHC] #10494: Representational equalities over AppTys are not hard failures

[GHC]

#10494: Representational equalities over AppTys are not hard failures
-------------------------------------+-------------------------------------
        Reporter:  goldfire          |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  high              |            Milestone:  7.10.3
       Component:  Compiler          |              Version:
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
                                     |  typecheck/should_compile/T10494
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by bgamari):

 * status:  merge => closed
 * resolution:   => fixed


Comment:

 The problem here is the fix seems to depend upon,
 {{{
 commit c1edbdfd9148ad9f74bfe41e76c524f3e775aaaa
 Author: Richard Eisenberg <eir at cis.upenn.edu>
 Date:   Mon Mar 23 10:30:19 2015 -0400

     Do proper depth checking in the flattener to avoid looping.

     This implements (roughly) the plan put forward in
 comment:14:ticket:7788,
     fixing #7788, #8550, #9554, #10139, and addressing concerns raised in
 #10079.
     There are some regressions w.r.t. GHC 7.8, but only with pathological
 type
     families (like F a = F a). This also (hopefully -- don't have a test
 case)
     fixes #10158. Unsolved problems include #10184 and #10185, which are
 both
     known deficiencies of the approach used here.

 }}}

 Which is quite a large patch and does not apply cleanly at all. Ultimately
 I think we'll need to punt on this one for 7.10.3.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10494#comment:13>
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