[GHC] #9792: map/coerce rule never seems to fire

[GHC]

#9792: map/coerce rule never seems to fire
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              Reporter:  dfeuer      |            Owner:  ekmett
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  7.10.1
             Component:  Core        |          Version:  7.9
  Libraries                          |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:  Runtime     |  Related Tickets:
  performance bug                    |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by goldfire):

 Forcing dictionary arguments to be strict helps here, but would that
 always work? For example, if we have

 {{{
 foo :: forall (c :: Constraint). c => Proxy c -> ()
 }}}

 would that still be inferred to be strict in its first (Core) parameter?

 Separately, I don't think my lifted/unlifted thoughts will have impact
 here, although the rewrite of the `Coercible` solver may. That task will
 begin shortly.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9792#comment:12>
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