Rule Proposal: no-unused-variables

[shadskii]

Please describe what the rule should do:
No unused computed properties or data.
What category of rule is this? (place an "X" next to just one item)

[X] Enforces code style
[ ] Warns about a potential error
[ ] Suggests an alternate way of doing something
[ ] Other (please specify:)

Provide 2-3 code examples that this rule will warn about:

<template>
    <h1>{{ used }}</h1>
</template>
<script>
export default {
    data(){
        return {
            unused: 0, //error
            used: 'Hello World!'
        }
    }
}
</script>

<template>
    <h1>{{ used }}</h1>
</template>
<script>
export default {
    computed: {
        used() {
            return 'Hello World';
        },
        unUsed() { //error
            return 'Unused';
        }
}
</script>

Why should this rule be included in ESLint (instead of a plugin)?
Unused computed properties and data makes Vue components difficult to read.

[phaibin]

Agree. This rule is very useful to check unused codes. Please add it ASAP!