[GHC] #9151: Recursive default associated types don't kind-generalize properly

[GHC]

#9151: Recursive default associated types don't kind-generalize properly
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        Reporter:  goldfire          |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.8.2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by archblob):

 Although my patch fixed this specific problem, it failed validation by
 causing others.
 My initial idea was to infer a more general {{{forall (a :: BOX). a ->
 *}}} kind when the associated type is mentioned in the rhs of the synonym,
 works for this case but causes breakages. Anyway, I'll be looking more
 into how to do it because I'm having a good time, but I'm not really sure
 anything will come of it so if someone else wants to work on this, don't
 mind me, go ahead.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9151#comment:8>
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