Svelte: Slot is not updated properly

[cvlab]

Describe the bug
create_default_slot is generated with newer assigned current variable.

To Reproduce
REPL:
https://svelte.dev/repl/c64a0a69c59544bda4a8a6dba3d0d13f?version=3.16.6

Select at least 2 times, span updates, img not.

        <span>img id:{ item.id }</span>
        <img src={ item.url } alt={ item.id }>

Investigation

Investigation

If current is undefined, img_src_value = and img_alt_value = are not assigned

// (2:0) <Nested items={ items.filter(item => item.author === value) } let:item>
function create_default_slot(ctx) {
...
    let current;

...
        p(ctx, dirty) {
            if ((!current || dirty & /*item*/ 128) && t2_value !== (t2_value = /*item*/ ctx[7].id + "")) set_data(t2, t2_value);

            if (!current || dirty & /*item*/ 128 && img.src !== (img_src_value = /*item*/ ctx[7].url)) {
                attr(img, "src", img_src_value);
            }

            if (!current || dirty & /*item*/ 128 && img_alt_value !== (img_alt_value = /*item*/ ctx[7].id)) {
                attr(img, "alt", img_alt_value);
            }
...
}

current condition generated in AttributeWrapper depends on block.has_outros
https://github.com/sveltejs/svelte/blob/cd21acfb3cae574b81f2f417331993374222a9de/src/compiler/compile/render_dom/wrappers/Element/Attribute.ts#L150

current assignment depends on intro.length and outro.length
https://github.com/sveltejs/svelte/blob/a8b306f0a18775b31b57333d938090eb3934eb29/src/compiler/compile/render_dom/Block.ts#L236

Here block.has_outros is true, but intro.length and outro.length is zero.

---

<Title> is crucial, it creates an instance of InlineComponentWrapper that calls block.add_outro()
https://github.com/sveltejs/svelte/blob/2cd5c2934b03c9ac3e5e984b3f1ccd3ffd657ef9/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts#L106
where has_outros became true for parent node, this has_outros generate current condition and varibale but not assignment
https://github.com/sveltejs/svelte/blob/a8b306f0a18775b31b57333d938090eb3934eb29/src/compiler/compile/render_dom/Block.ts#L196

Thanks!

[JohnnyFun]

If you use a keyed each block, it _seems_ to work:

{#each items as item (item.id)}

More info here: https://svelte.dev/tutorial/keyed-each-blocks

But that _does_ seem weird that it wouldn't just work otherwise. I'm running into a similar issue that I'm trying to boil down to simple REPL, but haven't been able to yet.

[JohnnyFun]

Fwiw, I also just noticed it seems to work if you get rid of the "title" slot. And similarly, works if you give the default slot a name.

Also works if you move the slot content to be the default slot content and then don't pass the component slot content.

Definitely some weirdness going on...

[tanhauhau]

Something wrong with the has_outro logic in the compiler.