[GHC] #11732: Deriving Generic1 interacts poorly with TypeInType

[GHC]

#11732: Deriving Generic1 interacts poorly with TypeInType
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        Reporter:  goldfire          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:  TypeInType,
                                     |  Generics
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 As I just wrote in the email thread: we can argue that GHC is inferring a
 `k ~ *` constraint on the `Cat` instance. With that understanding, we're
 not so poorly off here.

 Just a reminder to all: we've strayed quite far from the original ticket,
 which concerns a bespoke instantiation check for `Generic` and `Generic1`.
 So my "do nothing" comment does not mean we can just close the ticket.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11732#comment:15>
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