[GHC] #11594: closed empty type families fully applied get reduced lazily when in a constraint tuple and fully applied

[GHC]

#11594: closed empty type families  fully applied get reduced lazily when in a
constraint tuple and fully applied
-------------------------------------+-------------------------------------
        Reporter:  carter            |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler (Type    |              Version:  7.10.2
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9636             |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by goldfire):

 I think option (a) from comment:4 is the best way forward here: document
 `TypeError` more carefully. I will say that the feature is described in
 the manual in the section entitled `Custom compile-time errors`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11594#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler