rerun reactive declarations if the reactive declared variable is mutated

[tanhauhau]

Fixes #2444

The demo in #2444 was fixed in v3.2.1 but broken again since v3.16.0

The test case added in #2694 didn't handle a particular case in the demo where there's another declaration that should be invalidated too:

<script>
   let foo;
   $: var_a = some_fn(foo);
   $: var_b = some_fn(foo);
</script>
{#each var_b as b}
   <input bind:value={b} />
{/each}
{var_a.length} {var_b.length}

after #2694 mutating var_b, would $$invalidate var_b & foo.

but because foo wasn't mutated anywhere, var_a is marked as fixed_reactive_declarations instead, and $$invalidate foo will not produce a new var_a.

This fix is to mark foo as mutated if var_b or var_a is mutated.

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Tests

• Run the tests tests with npm test or yarn test)

[Conduitry]

The test failure here looks to be legitimate.

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[vercel]

@dummdidumm is attempting to deploy a commit to the Svelte Team on Vercel.

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[dummdidumm]

I'm not sure how I feel about this change.

• Con: It could result in a lot of false positive reruns
• Con: The tests currently fail, unsure how reliably we can get this to work with introducing bugs
• Pro: Intuitively it makes sense to me to rerun in this case

In general this looks like one of those general shortcomings / things we haven't quite thought through holistically for bindings. Personally I'd hold off from merging this and wait until Svelte 5 where we should have a deep conversation about the future direction of bindings.

[tanhauhau]

@dummdidumm yes you are right, i think we can hold off or even close this one for now.

[wackbyte]

now that Svelte 5 is out, it seems like this PR can be closed since the reactivity model has changed

[dummdidumm]

You're right, closing this