[GHC] #9995: :info enhancements

[GHC]

#9995: :info enhancements
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              Reporter:  shachaf     |             Owner:
                  Type:  feature     |            Status:  new
  request                            |         Milestone:
              Priority:  normal      |           Version:  7.8.4
             Component:  GHCi        |  Operating System:  Unknown/Multiple
              Keywords:              |   Type of failure:  None/Unknown
          Architecture:              |        Blocked By:
  Unknown/Multiple                   |   Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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 `:info` is a very useful ghci command, but there are several improvements
 that could be made:

 * It would be useful if `:i` showed not only which module a name is
 defined in, but which module(s) it was imported from in the current
 session.
 * A variant of `:i` that just prints a definition, rather than a
 definition and all instances, would be useful in many cases. E.g. `:i
 Show` prints the definition of `Show`, but then it prints so many
 instances that the definition is scrolled way off the screen.
 * `:i ->` is a parse error; it should behave like `:i (->)`, the way it
 works for other type-level operators.
 * hvr had some more suggestions: "finding out which package a module
 belongs to", "and what module an 'as'-alias is associated with".
 (Currently I think modules are out of `:info`'s scope, but perhaps it
 would be a useful addition.)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9995>
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