[GHC] #7543: Constraint synonym instances

[GHC]

#7543: Constraint synonym instances
-------------------------------------+-------------------------------------
        Reporter:  monoidal          |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.6.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by simonpj):

 Yes we could do as Richard suggests.  It'd be one more thing to explain in
 the user manual.  And I'm a little suspicious, because now if I'm hunting
 for instances of some class I need to take synonyms into account.

 I grant that we already allow ''type'' synonyms in the instance head, and
 that too makes hunting for instances harder in a similar way.

 Are these disadvantages outweighed by the advantages?  Do more than two
 people want this?

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7543#comment:8>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler