Fund: Rule proposal: `no-unused-reassignment`

Rule proposal: no-unused-reassignment

Prevent accidentally reassigning a variable and not using the result. It would only handle variables and reassignments in the same scope.

This is similar to no-unused-vars, but that rule doesn't handle this case.

It cannot auto-fix as getUnicorn() could be impure. We should at least provide a suggestion.

Fail

function foo() {
	let unicorn = getUnicorn();

	if (unicorn) {
		handleUnicorn(unicorn);
	}

	// …

	unicorn = getUnicorn();
}

let foo = 1;

// …

foo = 2;

// …

foo = 3;

console.log(foo);

function foo() {
	let unicorn = getUnicorn();

	if (unicorn) {
		handleUnicorn(unicorn);
	}
}

let foo = 1;

console.log(foo);