[GHC] #15798: Flag to warn when deriving strategy is not explicitly specified

[GHC]

#15798: Flag to warn when deriving strategy is not explicitly specified
-------------------------------------+-------------------------------------
        Reporter:  andrewthad        |                Owner:  (none)
            Type:  feature request   |               Status:  closed
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.6.1
      Resolution:  fixed             |             Keywords:  deriving,
                                     |  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
                                     |  rename/should_compile/T15798{a,b,c}
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |  https://gitlab.haskell.org/ghc/ghc/merge_requests/48
-------------------------------------+-------------------------------------
Changes (by RyanGlScott):

 * status:  new => closed
 * testcase:   => rename/should_compile/T15798{a,b,c}
 * differential:   => https://gitlab.haskell.org/ghc/ghc/merge_requests/48
 * resolution:   => fixed
 * milestone:   => 8.8.1


Comment:

 Landed in
 [https://gitlab.haskell.org/ghc/ghc/commit/c121e33f9b039acf2ac6939af8bfafe593560039
 c121e33f9b039acf2ac6939af8bfafe593560039]:

 {{{
 Author: chessai <chessai1996 at gmail.com>
 Date:   Wed Dec 26 12:12:37 2018 -0500

     Add -Wmissing-deriving-strategies

     Warn users when -XDerivingStrategies is enabled but not used, at each
     potential use site.

     add -Wmissing-deriving-strategies

     Reviewers: bgamari, RyanGlScott

     Subscribers: andrewthad, rwbarton, carter

     GHC Trac Issues: #15798

     Differential Revision: https://phabricator.haskell.org/D5451
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15798#comment:6>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler