Behaviours, defoverridable and implementations

[eproxus]

@josevalim

Unfortunately we cannot make it required because that would emit too many warnings. However, we can guarantee that, if you have used @impl true once in a module, you have to use it for all callback implementations.

This I don’t quite understand. You’re saying if @impl true shows up before just one of the callbacks, the others will be automatically given warnings? That either doesn’t make sense (you only wanted to implement one of the optional callbacks) or it could be done for all automatically (initiated by the use in the first place).

@josevalim

eproxus:
It also separates the behaviour inclusion into different parts in the module.

I am not sure I follow. The point is exactly to associate the usage of the behaviour with its implementation. The only way to keep it together would be with something like:

What I meant was that the intention to use a behaviour is now “shown” in two places, not just one (i.e. first the use and then the @impl. Wether that is a good or bad thing is subjective.

@OvermindDL1

Ooo, I actually quite like that to be honest… Maybe a defimplement or so? Or defoverride?

Yeah, I thought about something similar. Would it be possible to do def GenServer.handle_call(...)?

A list of the ideas in this thread so far:

@impl true
def handle_call(message, from, state) do
  # ...
end@impl GenServer

def handle_call(message, from, state) do
  # ...
end

defimpl handle_call(message, from, state) do
  # ...
end

def GenServer.handle_call(message, from, state) do
  # ...
end

impl GenServer do
  def handle_call(message, from, state) do
    # ...
  end
end