[GHC] #14333: GHC doesn't use the fact that Coercible is symmetric

[GHC]

#14333: GHC doesn't use the fact that Coercible is symmetric
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:  TypeFamilies,
                                     |  Roles
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 goldfire):

 Replying to [comment:7 simonpj]:
 > I found I could do this quite easily. (I happened to be in the area.)
 Patch coming.

 Ooh. I'm curious. I'm not yet ready to backtrack from my opinion that this
 would be hard.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14333#comment:9>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler