[GHC] #10642: Coercible regression from 7.10 to HEAD

[GHC]

#10642: Coercible regression from 7.10 to HEAD
-------------------------------------+-------------------------------------
        Reporter:  darchon           |                   Owner:  goldfire
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.11
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by Richard Eisenberg <eir@…>):

 In [changeset:"9f978b67212a51fa34ef44db463351b959ff15e4/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="9f978b67212a51fa34ef44db463351b959ff15e4"
 Fix #10642.

 Representational equalities cannot discharge nominal ones.
 Even if, somehow, this didn't cause a type error (as reported
 in the ticket), it would surely cause a core lint error.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10642#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler