[GHC] #11218: Provide `-W(no-)` aliases for `-f(no-)warn` warning flags

[GHC]

#11218: Provide `-W(no-)` aliases for `-f(no-)warn` warning flags
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        Reporter:  hvr               |                Owner:
            Type:  feature request   |               Status:  patch
        Priority:  high              |            Milestone:  8.0.1
       Component:  Compiler          |              Version:
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1613
       Wiki Page:  Design/Warnings   |
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Comment (by Herbert Valerio Riedel <hvr@…>):

 In [changeset:"2206fa8cdb1209320f3690690b610320b4810de6/ghc"
 2206fa8c/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="2206fa8cdb1209320f3690690b610320b4810de6"
 Add `-W(no-)xxx` aliases for `-f(no-)warn-xxx` flags

 This also updates the user's guide to refer to the `-W`-based warning
 flags by default.

 Quoting the release note entry:

 | Warnings can now be controlled with `-W(no-)...` flags in addition to
 | the old `-f(no-)warn...` ones. This was done as the first part of a
 | rewrite of the warning system to provide better control over warnings,
 | better warning messages, and more common syntax compared to other
 | compilers. The old `-fwarn...`-based warning flags will remain
 | functional for the forseeable future.

 This is part of
 https://ghc.haskell.org/wiki/Design/Warnings
 and addresses #11218

 Reviewed By: hvr, bgamari

 Differential Revision: https://phabricator.haskell.org/D1613
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11218#comment:3>
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