allow BindingPattern in FunctionRestParameter

[ajafff]

Second part of #6275

Also adds downlevel emit for the destructured rest param.
I don't know if my change emits correct sourcemaps. @weswigham how do you test this stuff?

[DanielRosenwasser]

Minor suggestion: can you put the tests in one file? Seems like they all could be there.

how do you test this stuff?

You can add a comment at the top of the file like

// @sourcemap: true

[ajafff]

I merged the new tests into one file and added baselines for sourceMap generation. I don't fully understand these baselines, but they don't look too wrong to me 😄

[mhegazy]

@weswigham can you please review and merge

[weswigham]

I'm blind, object binding tests are there: Could you enable sourcemaps on the one with object binding patterns, too? Also tests for initializers and type errors for object binding patterns, too.

[ajafff]

@weswigham can you please review again? I updated the PR according to your comment a while ago.

[ChiriVulpes]

Any news on this? I just ran into my first use case for it; now that there's nice tuple support I have some type aliases for tuples, it'd be nice to replace the function arguments with the existing tuple so it's updated if the tuple definition ever changes.

This would allow a method to be able to take a tuple or each value of the tuple easily, since if you're passing a tuple you just use the spread operator, whereas if you're passing the individual values it just works as is. Prevents having to construct new tuples with tuple = <T extends any[]>(...items: T) => items;

If you're curious, here's my Real World Code ™

type HighlightSelector = [HighlightType, string | number];

// in a class
public register(component: IComponent, selector: HighlightSelector, until = ComponentEvent.Remove) {
	const selectorId = this.getHighlightSelectorId(...selector);
	this.highlightComponents.set(selectorId, component);
	component.once(until, () => this.highlightComponents.delete(selectorId));
}

private getHighlightSelectorId(...[type, selector]: HighlightSelector) {
	return `${type}:${selector}`;
}

private getHighlightComponent([type, selector]: HighlightSelector) {
	if (type === HighlightType.Selector) {
		return Component.get(`${selector}`);
	}
	
	return this.highlightComponents.get(this.getHighlightSelectorId(type, selector));
}

[sheetalkamat]

Should this error still be there if its a object binding pattern?

[ajafff]

You mean something like (...{length}) => length? The spec allows it and there are already tests to ensure type inference and downlevel emit works as expected.