[GHC] #11974: `default` declaration doesn't allow higher-kinded types

[GHC]

#11974: `default` declaration doesn't allow higher-kinded types
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        Reporter:  goldfire          |                Owner:
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2136
       Wiki Page:                    |
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Comment (by goldfire):

 You're proposing a wholesale extension of the defaulting mechanism.
 Defaulting happens as per the Haskell Report or with a
 [https://downloads.haskell.org/~ghc/8.0.1-rc4/docs/html/users_guide/ghci.html
 #type-defaulting-in-ghci small extension]. In either case, the set of
 defaultable classes is fixed. You're proposing changing this, which is
 quite different than the purpose of this ticket. (This ticket is about
 letting `default` declarations include types that are already
 defaultable.) If you want this new behavior, I encourage you to write a
 specification of it (on a wiki page) and then submit a feature request.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11974#comment:5>
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