Exploring adding setWatch/clearWatch (interrupt handling) to MCP23017 (MCP2308) Portexpander Ports

• you know you can also do stuff like:...
  

And here it is this ... (from post #7):

(function() {
 var _setWatch = setWatch;
 setWatch = function(cb,pin,opts) {
   return (pin instanceof Pin)
    ? _setWatch(cb,pin,opts) // Espruino built-in pin class Pin
    : pin.setWatch(cb,opts); // Portexpander pin class PXP 
 };
}());

Espruino (you?) is(are) are not so happy with it - understandably:

Uncaught Error: Unable to assign value to non-reference Function
 at line 6 col 2
 };
 ^

If require() has the same issue, could you 'fix' that too? ...I'm milling around the require() as from require.js (requireJS.org - as it works in the browser) to make AMDs available on Espruino (via communication connection). Detection of alternative implementation is by number of arguments > 1).

If setWatch() cannot or should not be modified to become assignable, add a property to the options, add a property to the setWatch / clearWatch function that allows alternative implementations... for example:

setWatch.altImpls = { nonPinClass_1: alternativeImplementationFunciton_1, ... }
clearWatch.altImpls = { nonPinClass_1: alternativeImplementationFunciton_1, ... }