Re: [GHC] #8865: Cannot derive well-kinded instance of form ‘Category

[GHC]

#8865: Cannot derive well-kinded instance of form ‘Category
----------------------------------------------+----------------------------
        Reporter:  adinapoli                  |            Owner:
            Type:  bug                        |           Status:  closed
        Priority:  normal                     |        Milestone:  7.8.1
       Component:  Compiler                   |          Version:
      Resolution:  fixed                      |  7.8.1-rc2
Operating System:  MacOS X                    |         Keywords:
 Type of failure:  GHC rejects valid program  |     Architecture:  x86_64
       Test Case:                             |  (amd64)
        Blocking:                             |       Difficulty:  Unknown
                                              |       Blocked By:
                                              |  Related Tickets:
----------------------------------------------+----------------------------

Comment (by thoughtpolice):

 I'm somewhat inclined to think we actually should merge this. At the time
 the proposal to make `Category` PolyKinded was made, one of the nice parts
 was that it is essentially an invisible change to already existing code.
 In some sense I might argue that this is a regression, because while it
 involves a small 'change' that did not exist prior, it does cause GND over
 Category to fail in the wild, where it did not before.

 OTOH, I'm not sure how common the case of using GND to derive Category
 instances is - this is certainly the first time I've seen it.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8865#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler