[GHC] #16179: Mention DerivingStrategies in the warning when DeriveAnyClass and GeneralizedNewtypeDeriving are both enabled

[GHC]

#16179: Mention DerivingStrategies in the warning when DeriveAnyClass and
GeneralizedNewtypeDeriving are both enabled
-------------------------------------+-------------------------------------
           Reporter:  ckoparkar      |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:  8.10.1
          Component:  Compiler       |           Version:
           Keywords:  deriving       |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 When {{{DeriveAnyClass}}} and {{{GeneralizedNewtypeDeriving}}} are both
 enabled, GHC prints out the following warning for every {{{deriving C}}}:

 {{{
 #!haskell
 warning:
    • Both DeriveAnyClass and GeneralizedNewtypeDeriving are enabled
      Defaulting to the DeriveAnyClass strategy for instantiating C
 }}}

 Would it be useful to point the users to {{{DerivingStrategies}}} ?

 {{{Use DerivingStrategies to pick a different strategy}}}, or something
 similar? I'm not sure if this was already discussed before, I couldn't
 find any related tickets.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16179>
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