[GHC] #14045: Data family instances must list all patterns of family, despite documentation's claims to the contrary

[GHC]

#14045: Data family instances must list all patterns of family, despite
documentation's claims to the contrary
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.3
  checker)                           |
      Resolution:                    |             Keywords:  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #12369            |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by simonpj):

 * cc: goldfire (added)


Comment:

 To me the `k` argument to `Sing` looks like an invisible (implicit) one.
 So you should need visible kind application to use it in an invocation,
 something like
 {{{
 instance C (z :: Bool) where
   data Sing :: Bool -> Type where
     SFalse :: Sing @False
     STrue  :: Sing @True
 }}}
 Let's see what Richard says.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14045#comment:3>
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