fix head stuff

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

@@ -17,6 +17,7 @@ export const EFFECT_TRANSPARENT = 1 << 15;
 /** Svelte 4 legacy mode props need to be handled with deriveds and be recognized elsewhere, hence the dedicated flag */
 export const LEGACY_DERIVED_PROP = 1 << 16;
 export const INSPECT_EFFECT = 1 << 17;
+export const HEAD_EFFECT = 1 << 18;
 
 export const STATE_SYMBOL = Symbol('$state');
 export const STATE_FROZEN_SYMBOL = Symbol('$state.frozen');

packages/svelte/src/internal/client/dom/blocks/svelte-head.js

@@ -2,6 +2,7 @@ import { hydrate_anchor, hydrate_nodes, hydrating, set_hydrate_nodes } from '../
 import { empty } from '../operations.js';
 import { block } from '../../reactivity/effects.js';
 import { HYDRATION_END, HYDRATION_START } from '../../../../constants.js';
+import { HEAD_EFFECT } from '../../constants.js';
 
 /**
  * @type {Node | undefined}
@@ -47,7 +48,7 @@ export function head(render_fn) {
 	}
 
 	try {
-		block(null, 0, () => render_fn(anchor));
+		block(null, HEAD_EFFECT, () => render_fn(anchor));
 	} finally {
 		if (was_hydrating) {
 			set_hydrate_nodes(/** @type {import('#client').TemplateNode[]} */ (previous_hydrate_nodes));

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

@@ -31,7 +31,8 @@ import {
 	DERIVED,
 	UNOWNED,
 	CLEAN,
-	INSPECT_EFFECT
+	INSPECT_EFFECT,
+	HEAD_EFFECT
 } from '../constants.js';
 import { set } from './sources.js';
 import { remove } from '../dom/reconciler.js';
@@ -341,7 +342,7 @@ export function execute_effect_teardown(effect) {
 export function destroy_effect(effect, remove_dom = true) {
 	var removed = false;
 
-	if (remove_dom) {
+	if (remove_dom || (effect.f & HEAD_EFFECT) !== 0) {
 		var start = get_first_node(effect);
 		var end = get_last_node(effect);
 
@@ -391,7 +392,10 @@ export function get_first_node(effect) {
 	}
 
 	var child = effect.first;
-	while (child && (child.f & (BLOCK_EFFECT | BRANCH_EFFECT)) === 0) {
+	while (
+		child &&
+		((child.f & (BLOCK_EFFECT | BRANCH_EFFECT)) === 0 || (child.f & HEAD_EFFECT) !== 0)
+	) {
 		child = child.next;
 	}