[GHC] #14370: improve documentation of -fdefer-typed-holes for naked expressions in ghci

[GHC]

#14370: improve documentation of -fdefer-typed-holes for naked expressions in ghci
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        Reporter:  int-e             |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Documentation     |              Version:  8.2.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  error/warning at compile-time      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by sighingnow):

 I think that the `Opt_DeferOutOfScopeVariables` isn't cancelled for naked
 expression in ghci should be a bug. Allowing `length [r]` is also
 unhelpful and may lead to some confusion for newcomers. I think this
 should be fixed as well.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14370#comment:5>
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