compile error when reactive statement will never change

[DetachHead]

Describe the problem

<script>
	let _value = ''
	$: value = getValue()
	
	const getValue = () => _value
</script>

<input bind:value={_value}>
<p>value: {value}</p>

here, the $: is being used incorrectly as it will not be re-run when _value changes, because there are no variables that will change being referenced

when learning svelte, i ran into issues like this several times, so i think there should be a compiler error/warning when reactive statements are used incorrectly like this

Describe the proposed solution

a compiler error/warning if all of the variables referenced in a reactive statement are immutable

Alternatives considered

eslint-plugin-svelte rule, but i think this would be better handled by the svelte compiler because it's first party

Importance

would make my life easier

[baseballyama]

Previously, we discussed this point.

#7942 (comment)

[dummdidumm]

From that comment:

We discussed with maintainers and concution is that we should not implement warnings because the compiler might analyse that it's unnecessary, but the user might have this deliberately:

e.g.

<script>
  export const foo = 1;
  export const bar = 1;
  export const baz = 1;

  // For now, all dependencies are static, but maybe in the future, one or more variables will be dynamic.
  // So intentionally, people could use `$:` here to prevent a bug later
  $: qux = foo + bar + baz;
</script>

Therefore closing