Re: [GHC] #14111: strange error when using data families with levity polymorphism and unboxed sums and data families

13 Aug 2017

      #14111: strange error when using data families with levity polymorphism and unboxed
sums and data families
-------------------------------------+-------------------------------------
        Reporter:  carter            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      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 carter):

 remarkably, if i add the type annotation, this works! (but it still seems
 like a bug in inference)

 {{{

 data instance Maybe (x :: TYPE 'UnliftedRep) where
   MaybeSumU :: (# x | (# #) #) -> Maybe (x :: TYPE 'UnliftedRep)
 }}}
 it seems kinda redundant ??

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14111#comment:1
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler