Glob assignment of private fields fails

[bbrk24]

trafficstars

The following code attempts to incorrectly destructure this:

class Foo
  #x = 0
  #y = 0

  clone()
    return = new Foo
    return.value{#x,#y} = @

class Foo {
  #x = 0;
  #y = 0;

  clone() {
    let ret;
    ret = new Foo();
    ({ x: ret.#x, y: ret.#y } = this);
    return ret;
  }
}

I don't think it's possible to destructure private fields.

[STRd6]

It looks like we'll need to do these manually. 😿

https://github.com/tc39/proposal-destructuring-private

[edemaine]

Until then, we could rewrite this as follows:

return.value{#x,#y} = @
↓↓↓
({ x: ret.#x, y: ret.#y } = { x: this.#x, y: this.#y });

Of course, if we had something like return.value{x,#x} = this, we'd have to do some more renaming...

Maybe worth implementing a general form of the TC39 proposal-destructuring-private spec at the same time.

[bbrk24]

We could always use quoted keys:

({ "#x": ret.#x, "#y": ret.#y } = { "#x": this.#x, "#y": this.#y });

I suppose it's still possible to collide with non-private fields but I don't imagine ret{#x,"#x"} = @ to be a very common situation...

[STRd6]

I think we would instead do something like:

ret.#x = this.#x, ret.#y = this.#y;

Essentially pollyfilling without destructuring ourselves. We may need to consider what to do if there is an additional chained assignment but erroring in that case is probably fine.