Exhibit A: > With -XDeriveDataTypeable, you can derive instances of the class Data, defined in Data.Data. See "Deriving Typeable instances" for deriving Typeable.
Exhibit B: > -XDeriveDataTypeable > Enable automatic deriving of instances for the Typeable typeclass Exhibit C: > Derived instances of Typeable are ignored, and may be reported as an error in a later version of the compiler. ---------------- A and B seem contradictory: Is this extension for deriving Data, or for deriving Typeable? B and C seem... not technically contradictory, but why is there an extension that enables the deriving of instances that will just be ignored? Is this extension meant to be deprecated? >From experimentation, it seems like all types automatically get Typeable instances whether you declare it or not. Is that accurate?
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