Create a macro for properly setting builtin member functions

[IovoslavIovchev]

When creating a new member function for some builtin, you need to make sure the create_constructor() function contains this:

let some_func = to_value(func as NativeFunctionData);
some_func.set_field_slice("length", to_value(1_i32));

// .. and then
some_prototype.set_field_slice("someFunc", some_func); 

Writing these two lines for each new function can prove tedious and error prone, as the second line can be missed when needed (functions have their length property reflect the number of arguments they accept).

What I propose is the following macro:

make_fn!(some_func, named "someFunc", with length 1, of some_prototype);

which will essentially contain the 3 aforementioned boilerplate lines.

What I am saying should definitely not be set in stone. It is only supposed to start a discussion on the topic.

[jasonwilliams]

This is a good idea, although i wonder if it will overlap Function Objects

Would this macro only be used for built-in functions? Or would you see it being used for functions we come across in code?

[IovoslavIovchev]

Depends on what you mean by "functions we come across in code".
My intention is for it to only be used for reducing boilerplate in buil-tins.

It is a more humble version of CreateBuiltinFunction (of which I found no implementation, apologies if I missed anything) but for properties, rather than internal slots.
Of course, we could expand the scope a bit here and fully implement CreateBuiltinFunction.

[jasonwilliams]

I'm happy to push ahead with this, we can always change it as need be.
I think itl prove useful

[IovoslavIovchev]

Great. I believe it will be a good first issue.

Will mark it as such, if anyone is interested.

[Stupremee]

I can take care of this

[Stupremee]

This issue can be closed I guess

[IovoslavIovchev]

Done as part of #206

[thiagoarrais]

I'm getting undefined when I do 'abc'.matchAll.length in tests.js. Even after upgrading to 7698873. Am I doing something wrong?

[Stupremee]

I think a new issue for your issue would be better @thiagoarrais

[thiagoarrais]

Sure!