Re: [GHC] #14070: Allow ‘unsafe’ deriving strategy, deriving code with ‘unsafeCoerce’

[GHC]

#14070: Allow ‘unsafe’ deriving strategy, deriving code with ‘unsafeCoerce’
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
                                     |  QuantifiedContexts
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 Iceland_jack):

 I will respond in full in a bit but

 Replying to [comment:7 RyanGlScott]:

 > This is important, since the `f` needs to scope over both `x` and `x'`.
 In your example, the `f` tucked underneath the two occurrences of the
 `Lens` type synonyms were distinct.

 Ah yes, the million ISK question is whether GHC can coerce that
 automatically: or does that enter `ImpredicativeTypes` territory?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14070#comment:9>
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