Named Function Arguments with defaults and - Feature Proposal

[gotjoshua]

This feature request is continuing a discussion here:
#2645 (comment)

I feel that the current way to define named arguments and give them defaults, could use some improvement, so I offer a proposal here to discuss some possibilities. I'd like it to work as close to ECMA as possible:

11.1.1 Default parameter values

function func(x, y=0) {
    return [x, y];
}
func(1, 2); // [1, 2]
func(1); // [1, 0]
func(); // [undefined, 0]

I know this precise syntax won't work in fish, but perhaps something like this:

function func -a x, y=0
    return [x, y];
end;

I also thought about making required or optional explicit could be handy (and fish could offer automatic errors when the func is called without required params, eg:

function func --argument-required x --argument-optional y=0
    return [x, y];
end;
func 1 2; // [1, 2]
func 1; // [1, 0]
func null 1; // [null,1]  *does fish understand 'null'?
func; // error: argument x is required

Perhaps it could have a short-form like:

function func -ar x -ao y=0
    return [x, y];
end;

-o and -r would be irrelevant if used without -a

I have zero experience with C code, so I doubt it is me to set up a dev and build environment to play with this, but I am very happy to discuss the details of how we may like the feature to function, and to come in contact with the project maintainers. I think Fish Shell seriously rocks, and I'm happy to help make it better.

[gotjoshua]

centuries later, i see a fair number of reactions on this...

and i must admit i don't know the state of the art.

Is this still a valid request?
or is there a recommended modern fishy way to accomplish the same?