[GHC] #14932: DeriveAnyClass produces unjustifiably untouchable unification variables

[GHC]

#14932: DeriveAnyClass produces unjustifiably untouchable unification variables
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.4.1
  checker)                           |
      Resolution:                    |             Keywords:  deriving
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13272, #14933    |  Differential Rev(s):  Phab:D4507
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by RyanGlScott):

 I'm biased, but I think so. I'm amazed `DeriveAnyClass` was working
 correctly at all before this patch! (Plus, the patch looks larger than it
 really is—at its core, it's quite small.)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14932#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler