Fix runtime effect issues

packages/svelte/src/compiler/phases/3-transform/client/utils.js

@@ -251,6 +251,8 @@ export const function_visitor = (node, context) => {
 		const in_constructor = parent.type === 'MethodDefinition' && parent.kind === 'constructor';
 
 		state = { ...context.state, in_constructor };
+	} else {
+		state = { ...context.state, in_constructor: false };
 	}
 
 	if (metadata?.hoistable === true) {

packages/svelte/src/internal/client/runtime.js

@@ -343,7 +343,13 @@ function destroy_references(signal) {
 	if (references !== null) {
 		let i;
 		for (i = 0; i < references.length; i++) {
-			destroy_signal(references[i]);
+			const reference = references[i];
+			if ((reference.flags & IS_EFFECT) !== 0) {
+				destroy_signal(reference);
+			} else {
+				remove_consumer(reference, 0, true);
+				reference.dependencies = null;
+			}
 		}
 	}
 }
@@ -710,7 +716,7 @@ export function exposable(fn) {
 export function get(signal) {
 	const flags = signal.flags;
 	if ((flags & DESTROYED) !== 0) {
-		return /** @type {V} */ (UNINITIALIZED);
+		return signal.value;
 	}
 
 	if (is_signal_exposed && current_should_capture_signal) {
@@ -1156,6 +1162,11 @@ export function managed_pre_effect(init, sync) {
  * @returns {import('./types.js').EffectSignal}
  */
 export function pre_effect(init) {
+	if (current_effect === null) {
+		throw new Error(
+			'The Svelte $effect.pre rune can only be used during component initialisation.'
+		);
+	}
 	const sync = current_effect !== null && (current_effect.flags & RENDER_EFFECT) !== 0;
 	return internal_create_effect(
 		PRE_EFFECT,

packages/svelte/tests/runtime-runes/samples/class-state-constructor-closure-private/_config.js

@@ -0,0 +1,13 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	html: `<button>10</button>`,
+	ssrHtml: `<button>0</button>`,
+
+	async test({ assert, target }) {
+		flushSync();
+
+		assert.htmlEqual(target.innerHTML, `<button>10</button>`);
+	}
+});

packages/svelte/tests/runtime-runes/samples/class-state-constructor-closure-private/main.svelte

@@ -0,0 +1,14 @@
+<script>
+	class Counter {
+		count = $state(0);
+
+		constructor() {
+			$effect(() => {
+				this.count = 10;
+			});
+		}
+	}
+	const counter = new Counter();
+</script>
+
+<button on:click={() => counter.count++}>{counter.count}</button>

packages/svelte/tests/runtime-runes/samples/class-state-constructor-closure/_config.js

@@ -0,0 +1,13 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	html: `<button>10</button>`,
+	ssrHtml: `<button>0</button>`,
+
+	async test({ assert, target }) {
+		flushSync();
+
+		assert.htmlEqual(target.innerHTML, `<button>10</button>`);
+	}
+});

packages/svelte/tests/runtime-runes/samples/class-state-constructor-closure/main.svelte

@@ -0,0 +1,22 @@
+<script>
+	class Counter {
+		#count = $state(0);
+
+		constructor() {
+			$effect(() => {
+				this.#count = 10;
+			});
+		}
+
+		getCount() {
+			return this.#count;
+		}
+
+		increment() {
+			this.#count++;
+		}
+	}
+	const counter = new Counter();
+</script>
+
+<button on:click={() => counter.increment()}>{counter.getCount()}</button>

packages/svelte/tests/runtime-runes/samples/effect-cleanup/_config.js

@@ -0,0 +1,19 @@
+import { test } from '../../test';
+import { flushSync } from 'svelte';
+
+export default test({
+	get props() {
+		return { log: [] };
+	},
+
+	async test({ assert, target, component }) {
+		const [b1] = target.querySelectorAll('button');
+		flushSync(() => {
+			b1.click();
+		});
+		flushSync(() => {
+			b1.click();
+		});
+		assert.deepEqual(component.log, ['init 0', 'cleanup 2', 'init 2', 'cleanup 4', 'init 4']);
+	}
+});

packages/svelte/tests/runtime-runes/samples/effect-cleanup/main.svelte

@@ -0,0 +1,17 @@
+<script>
+	const {log} = $props();
+
+	let count = $state(0);
+
+	$effect(() => {
+		let double = $derived(count * 2)
+
+		log.push('init ' + double);
+
+		return () => {
+			log.push('cleanup ' + double);
+		};
+	})
+</script>
+
+<button on:click={() => count++ }>Click</button>