[GHC] #10760: Conflicting typefamily instances not reported with polykinds

[GHC]

#10760: Conflicting typefamily instances not reported with polykinds
-------------------------------------+-------------------------------------
        Reporter:  steely            |                   Owner:
            Type:  bug               |                  Status:  closed
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.8.3
      Resolution:  invalid           |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  GHC accepts       |  Unknown/Multiple
  invalid program                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------
Changes (by goldfire):

 * status:  new => closed
 * resolution:   => invalid


Comment:

 This is correct behavior. All kind variables in a type family are always
 inputs. This is admittedly counter-intuitive when the kind variable
 classifies the result. If we write kinds explicitly, your example becomes
 this:

 {{{
 type family   Bar k        (a :: *) :: k
 type instance Bar *        Int      = Int
 type instance Bar (* -> *) Int      = []
 }}}

 If you have a concrete suggestion of how to improve the manual in this
 regard, we'd love to have it.

 Thanks for reporting!

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10760#comment:1>
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