Support methods as actions ( use:obj.action )

[pushkine]

I'd like to suggest making methods valid actions that keep their contextual this, such as to make the following code valid :

<script>
	const obj = { 
		foo : "bar",
		action(element, { leet }) {
			console.log(this.foo); // "bar"
		},
	 }
</script>

<div use:obj.action={{ leet: 1337 }} />

It happens that some cross component functionality can only [is more convenient to] be applied through actions, in those situations one may want to bundle it all in an object or a class with action methods directly applying the relevant state.

Unfortunately methods must at least be destructured and optionally bound to the relevant object before being used, all in seemingly unnecessary boilerplate repeated across every component

While const obj_action = obj.action.bind(obj); in the script block or the class constructor is not the end of the world, it still acts on readability, performance, bundle size and memory consumption, not to mention the ReturnType of bind is always any in typescript

Supporting object methods as actions requires the following changes

• Allow action functions to be a MemberExpression whose object and property are both Identifiers ( currently only accepts a single Identifier )
• Pass MemberExpression.object in the block ctx and call the relevant property name on mount

- /* obj.action */ ctx[0].call(null, div, { leet: 1337 });
+ /* obj */        ctx[0].action(div, { leet: 1337 });

[Conduitry]

Duplicate of #3935, although this one does have a better explanation.