Fix false positives for uninitialized vars in vue/no-ref-as-operand rule

[ota-meshi]

close #1980

[jacekkarczmarczyk]

Not sure about the PR implementation, but I think the title is wrong - it's not only about "uninitialized" variables, it's about variables that are Ref | NotARef, for example

let foo: Ref<number> | number = 5;

foo = ref(3);

is also "fixed" to

const foo: Ref<number> | number = 5;

foo.value = ref(3);

even though variable is initialized

[ota-meshi]

I am not familiar with English. Could you suggest a title?

The example you provided seems to work fine when I checked it on the demo site.

<script lang="ts">
import { ref } from 'vue'
let foo: Ref<number> | number = 5;

foo = ref(3);
</script>

https://deploy-preview-1988--eslint-plugin-vue.netlify.app/rules/no-ref-as-operand.html

[jacekkarczmarczyk]

I'm not native english neither, but I think that issue title describes the problem fine and might be used as a PR title too

[ota-meshi]

The rule will report it if:

<script lang="ts">
import { ref } from 'vue'
let foo: Ref<number> | number = ref(3);

foo = 5;
</script>

(If you think this is a false positive, I recommend turning off the rule.)

So I think Ref | NotARef doesn't show the correct meaning.

[jacekkarczmarczyk]

I see your point. I'm not really sure if your code should report the error, however suggestion to turn the rule off seems to make sense as the problem would be reported by TS anyway, at least in this case (and that's actually how I've found out the problem, if not TS I might have missed it and end up with incorrect code).

On the other hand there are cases where TS wouldn't spot the error, e.g.

let t: Ref|number = ref(5);
function fn () {
  if (t > 3) t = 1;
}

I'm investigating this issue now