fix: cleanup each items in legacy mode

Author: paoloricciuti

.changeset/honest-rabbits-glow.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: cleanup `each` items in legacy mode

packages/svelte/src/internal/client/dom/blocks/each.js

@@ -32,7 +32,12 @@ import {
 	pause_effect,
 	resume_effect
 } from '../../reactivity/effects.js';
-import { source, mutable_source, internal_set } from '../../reactivity/sources.js';
+import {
+	source,
+	mutable_source,
+	internal_set,
+	remove_from_legacy_sources
+} from '../../reactivity/sources.js';
 import { array_from, is_array } from '../../../shared/utils.js';
 import { INERT } from '#client/constants';
 import { queue_micro_task } from '../task.js';
@@ -549,7 +554,16 @@ function create_item(
 	current_each_item = item;
 
 	try {
-		item.e = branch(() => render_fn(anchor, v, i, get_collection), hydrating);
+		item.e = branch(() => {
+			render_fn(anchor, v, i, get_collection);
+			// we only need to clean this up if the item is reactive and mutable
+			// because that's when we add the source to the context preventing garbage collection of it
+			if (reactive && mutable) {
+				return () => {
+					remove_from_legacy_sources(item.v);
+				};
+			}
+		}, hydrating);
 
 		item.e.prev = prev && prev.e;
 		item.e.next = next && next.e;

packages/svelte/src/internal/client/reactivity/sources.js

@@ -112,6 +112,15 @@ export function mutable_source(initial_value, immutable = false) {
 	return s;
 }
 
+/**
+ * @param {Source} source
+ */
+export function remove_from_legacy_sources(source) {
+	if (component_context?.l?.s) {
+		component_context.l.s = component_context.l.s.filter((s) => s !== source);
+	}
+}
+
 /**
  * @template V
  * @param {Value<V>} source