[GHC] #11008: Difficulties around inferring exotic contexts

[GHC]

#11008: Difficulties around inferring exotic contexts
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        Reporter:  crockeea          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 I think our algorithms are the same. Mine accepts your original example,
 because it simplifies `Eq (Foo r)` to get `C (F r)`, so in my terminology,
 `C (F r)` is considered "simplified".

 Now that we have an idea of what we're talking about, we can think about
 whether or not it is actually a good idea.

 I'm inclined to think it is.

 One tiny, easily-surmountable wrinkle is that we'd need to check for
 `FlexibleContexts` and/or `UndecidableInstances` and/or ... before
 accepting the constraint. But that's fairly routine.

 I'd want Simon's opinion on this before rubber stamping it. And then
 there's the matter of implementation.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11008#comment:9>
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