For function return types: Use "unknown", not "void" or "any"

return_type.tsx

// when passing functions as props and you don't care about the return value, use "unknown"

type Props = {
    onUpdate: () => unknown; // Use "unknown"!
};
function Component({onUpdate}: Props) {
 	return <button onClick={onUpdate}>update</button>
}

// With "unknown", both of these are valid!
function updateNoReturn() {
	doSomething(); // notice, no return
}
function updateWithReturn() {
 	return doSomething(); 
}
<Component onUpdate={updateNoReturn} /> // OK!
<Component onUpdate={updateWithReturn} /> // OK!
 

// Why not "void"?

type Props = {
	onUpdate: () => void; 
}
<Component onUpdate={updateNoReturn} /> // OK!
<Component onUpdate={updateWithReturn} /> // ERROR!