[GHC] #13039: Add options to select GHCi prompt type errors

[GHC]

#13039: Add options to select GHCi prompt type errors
-------------------------------------+-------------------------------------
           Reporter:  dfeuer         |             Owner:
               Type:  feature        |            Status:  new
  request                            |
           Priority:  low            |         Milestone:  8.4.1
          Component:  GHCi           |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 [This SO post](http://stackoverflow.com/questions/41354231/how-can-i-set-
 up-haskells-ghci-to-interactively-evaluate-functions-to-their-sig)
 implicitly suggests some extra options for reporting type errors for
 expressions typed into GHCi. When GHCi reports a type error for an
 expression `e` typed at the prompt, it has effectively failed to check
 `void e :: IO ()` and `print e :: IO ()`. It always reports the error for
 the latter. There are three things a user may want, and I think options
 should control which ones are shown:

 1. Why didn't `void e :: IO ()` check?

 2. Why didn't `print e :: IO ()` check?

 3. If any type could be inferred for `e`, what was it?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13039>
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