On Arduino, you'll tipically declare a new callback on the main file for each thing you are listening on.

It's very difficult to write generic, reusable libraries that attach to interruptions or other callbacks.

In C/C++ world, we usually specify an extra void* parameter when registering the callback, where the listener can store any context necessary.

I suggest we adopt this on all Arduino callbacks: attachInterrupt(), Serial.serialEvent(), Wire.OnReceive(), etc

I've already create #4519, which upgrades attachInterrupt().

Keep in mind that the changes can be done in a backwars-compatible way, and the impact in performance, memory and flash storage is quite low (But not zero)