Re: [GHC] #14157: Flipping (give :: a -> (Given a => r) -> r) has type (r -> a -> r)

26 Aug 2017


      #14157: Flipping (give :: a -> (Given a => r) -> r) has type (r -> a -> r)
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      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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Changes (by RyanGlScott):

 * cc: RyanGlScott (added)


Comment:

 This isn't limited to `flip`, since you can also trigger similar behavior
 with a simple redefinition of `give`:

 {{{
 GHCi, version 8.2.1: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/ryanglscott/.ghci
 λ> :set -XRankNTypes
 λ> class Given a
 λ> let give :: a -> (Given a => r) -> r; give = undefined
 λ> let f x y = give x y
 λ> :type +v f
 f :: a -> p -> p
 λ> :type f
 f :: a -> p -> p
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14157#comment:2
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