[GHC] #10116: Closed type families: Warn if it doesn't handle all cases

[GHC]

#10116: Closed type families: Warn if it doesn't handle all cases
-------------------------------------+-------------------------------------
        Reporter:  andrewthad        |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.8.4
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by rwbarton):

 This might fall out of the implementation anyways, but a special case to
 be aware of is non-exhaustiveness in implicit kind variables, such the
 return kind of a polykinded type family, as arose in #11275:
 {{{
 type family Hm :: k where Hm = Int
 }}}
 Despite appearances this type family is not exhaustive: `Hm :: (* -> *)`
 will not reduce.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10116#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler