[GHC] #15290: QuantifiedConstraints: panic "addTcEvBind NoEvBindsVar"

[GHC]

#15290: QuantifiedConstraints: panic "addTcEvBind NoEvBindsVar"
-------------------------------------+-------------------------------------
        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
                                     |  QuantifiedConstraints
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:  quantified-
                                     |  constraints/T15290, T15290a
      Blocked By:                    |             Blocking:  9123
 Related Tickets:                    |  Differential Rev(s):  Phab:D4895
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by RyanGlScott):

 Replying to [comment:32 simonpj]:
 > Are we done now?

 I certainly hope so! :) I've rebased Phab:D4895 on top of your most recent
 changes, so that should wrap things up on this ticket.

 Another question remains of what to do with #9123, which requests that
 `GeneralizedNewtypeDeriving` emit quantified constraints involving
 `Coercible`. But this ticket shows that doing so often leads to disaster.
 In light of this, should we close #9123 as wontfix?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15290#comment:33>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler