[GHC] #16248: ImplicitParams does not imply FlexibleContexts or FlexibleInstances

[GHC]

#16248: ImplicitParams does not imply FlexibleContexts or FlexibleInstances
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        Reporter:  NeilMitchell      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Documentation     |              Version:  8.6.3
      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 NeilMitchell):

 To clarify the logic I'm using here: The above code requires
 TypeSynonymInstances, FlexibleInstances and ImplicitParams. To
 successfully compile, the minimum number of extensions I can write is
 ImplicitParams and FlexibleInstances. TypeSynonymInstances is not
 required.

 GHC claims that FlexibleInstances implies TypeSynonymInstances, and
 ImplicitParams implies FlexibleInstances. As a consequence
 FlexibleInstances should definitely be unnecessary. But it is required, so
 the docs are buggy.

 I had implicitly assumed that implications were transitive. Whether they
 are or not, the ImplicitParams still doesn't appear to imply
 FlexibleInstances. It would be good to document this detail in the
 documentation.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16248#comment:2>
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