Again, I’m not advocating for the macro, at all, in any way shape or form. I agree in this case it’s not needed. I’m contrasting the approaches taken between GenServer and HTTPoison.Base.
https://github.com/elixir-lang/elixir/blob/master/lib/elixir/lib/gen_server.ex#L760
vs.
https://github.com/edgurgel/httpoison/blob/master/lib/httpoison/base.ex#L220
Dialyzer will pick this all up even if you drop all the @specs. But for readers of the code, giving them the ability to @spec the implementation is much more pleasant (even if they choose not to), because they do not need to look outside the file or inside IEx to be able to figure out what’s going on. And if they have the Credo rule on to require @spec for all functions, you must ignore in the implementation because the compiler will complain about duplicate specs for the implemented callbacks.
