[GHC] #12625: Bad error message for flags with required but missing arguments

[GHC]

#12625: Bad error message for flags with required but missing arguments
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           Reporter:  dramforever    |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           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:
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 {{{
 $ ghc -I
 ghc: unrecognised flag: -I
 did you mean one of:
   -I
   -F
   -v

 Usage: For basic information, try the `--help' option.
 }}}

 Which is confusing (Unrecognized `-I`. Did you mean `-I`?), and not
 informative (No mention of the missing argument)

 I expect something like "missing argument for `-I`", or a basic usage info
 on `-I` instead.

 It looks similar to #9776 to me.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12625>
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