Re: [GHC] #14661: Cannot derive (newtype I a b = I (F a -> F b) deriving newtype Category) for type family F

12 Jan 2018

      #14661: Cannot derive (newtype I a b = I (F a -> F b) deriving newtype Category)
for type family F
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.4.1-alpha1
      Resolution:                    |             Keywords:
                                     |  DerivingStrategies, deriving,
                                     |  TypeFamilies
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 simonpj):
...
Well sure—you can't use GeneralizedNewtypeDeriving on a non-newtype
The newtype is called `Ixed`.  The type function is `Interp`. Turning it
 into a data type (and removing the instances) simplifies the example, but
 does not affect the payload.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14661#comment:8
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