Hi,

(I also asked on Stackoverflow, I hope cross-posting is ok.)

I expected it to be documented in Module, probably with references to structs, but no joy. Seen it used with a single or a list of arguments. All the variations I could find so far:

• list of module names such as
  @derive [MyProtocol, Another]

  (e.g., Kernel.defstruct/1 macro doc,
  line 65 in ProtocolTest (v1.7.4))

• module name such as
  @derive Inspect

• tuple in the form of
  @derive {Protocol, key1: :val1, :others}

  (e.g., line 550 in InspectTest (v1.8.0-rc.0),
  Phoenix.Param protocol doc)

• list of tuples such as
  @derive [{Prot1, :options}, {Prot2, key: :val}]

  (e.g., line 225 in ProtocolTest (v1.7.4))

The only places I found mentions of @derive:

• “Deriving” section in the documentation of Kernel.defstruct/1 macro
• New (i.e., v1.8.0-rc.0) “Deriving” section of Inspect
• Documentation of Protocol.derive/3 macro (added in #7019)
  (This was extremely helpful because using the example snippets one can test all the combinations above.)

Wasn’t sure whether I’m not just overlooking something, therefore didn’t open an issue or pull request.