function update_legacy_props($$new_props) {
	for (var key in $$new_props) {
		if (key in this) {
			this[key] = $$new_props[key];
		}
	}
}
Used to simulate `$set` on a component instance when `compatibility.componentApi === 4`.
Needs component accessors so that it can call the setter of the prop. Therefore doesn't
work for updating props in `$$props` or `$$restProps`.
@this {Record<string, any>}
@param {Record<string, any>} $$new_props