[GHC] #15351: QuantifiedConstraints ignore FunctionalDependencies

[GHC]

#15351: QuantifiedConstraints ignore FunctionalDependencies
-------------------------------------+-------------------------------------
        Reporter:  aaronvargo        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.5
  checker)                           |             Keywords:
      Resolution:                    |  QuantifiedConstraints
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by simonpj):

 > How difficult would it be?

 The logic for top-level instances is in `TcInteract.doTopReactDict`: see
 `try_fundep_improvement`. You want to do something similar for the local
 quantified constraints.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15351#comment:11>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler