[GHC] #14357: Document deriving strategies fully

[GHC]

#14357: Document deriving strategies fully
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Documentation     |              Version:  8.2.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by nomeata):

 Sure, good documentation is tricky :-)

 I would have found the enumeration at the beginning of the wiki section
 already quite useful.

 Also note that this describes what happens without `DerivingStrategies`.
 So maybe it should not be documented under this language extension… Bits
 of the information that is missing here are scattered throughout the
 documentation, e.g.
 https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html
 #precise-gnd-specification states:

 > Lastly, all of this applies only for classes other than Read, Show,
 Typeable, and Data, for which the stock derivation applies (section 4.3.3.
 of the Haskell Report).

 So maybe there should be a general section that describes GHC’s approach
 to deriving more general, and gives an overview that spans the various
 pragmas.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14357#comment:2>
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