chore: more signal fine-tuning (#9531)

* chore: opt for two signal data-structures to reduce memory usage

Author: trueadm

.changeset/hungry-dots-fry.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+chore: more signal perf tuning

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

@@ -14,21 +14,21 @@ export const global_visitors = {
 	},
 	MemberExpression(node, { state, next }) {
 		if (node.object.type === 'ThisExpression') {
-			// rewrite `this.#foo` as `this.#foo.value` inside a constructor
+			// rewrite `this.#foo` as `this.#foo.v` inside a constructor
 			if (node.property.type === 'PrivateIdentifier') {
 				const field = state.private_state.get(node.property.name);
 
 				if (field) {
-					return state.in_constructor ? b.member(node, b.id('value')) : b.call('$.get', node);
+					return state.in_constructor ? b.member(node, b.id('v')) : b.call('$.get', node);
 				}
 			}
 
-			// rewrite `this.foo` as `this.#foo.value` inside a constructor
+			// rewrite `this.foo` as `this.#foo.v` inside a constructor
 			if (node.property.type === 'Identifier' && !node.computed) {
 				const field = state.public_state.get(node.property.name);
 
 				if (field && state.in_constructor) {
-					return b.member(b.member(b.this, field.id), b.id('value'));
+					return b.member(b.member(b.this, field.id), b.id('v'));
 				}
 			}
 		}

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

@@ -26,7 +26,6 @@ import {
 	EACH_IS_CONTROLLED,
 	EACH_INDEX_REACTIVE,
 	EACH_ITEM_REACTIVE,
-	EACH_IS_ANIMATED,
 	PassiveDelegatedEvents,
 	DelegatedEvents
 } from '../../constants.js';
@@ -624,7 +623,7 @@ export function bind_playback_rate(media, get_value, update) {
 	// Needs to happen after the element is inserted into the dom, else playback will be set back to 1 by the browser.
 	// For hydration we could do it immediately but the additional code is not worth the lost microtask.
 
-	/** @type {import('./types.js').Signal | undefined} */
+	/** @type {import('./types.js').ComputationSignal | undefined} */
 	let render;
 	let destroyed = false;
 	const effect = managed_effect(() => {
@@ -2083,7 +2082,7 @@ export function update_each_item_block(block, item, index, type) {
 	if (transitions !== null && (type & EACH_KEYED) !== 0) {
 		let prev_index = block.index;
 		if (index_is_reactive) {
-			prev_index = /** @type {import('./types.js').Signal<number>} */ (prev_index).value;
+			prev_index = /** @type {import('./types.js').Signal<number>} */ (prev_index).v;
 		}
 		const items = block.parent.items;
 		if (prev_index !== index && /** @type {number} */ (index) < items.length) {
@@ -2125,7 +2124,7 @@ export function destroy_each_item_block(
 		if (!controlled && dom !== null) {
 			remove(dom);
 		}
-		destroy_signal(/** @type {import('./types.js').Signal} */ (block.effect));
+		destroy_signal(/** @type {import('./types.js').EffectSignal} */ (block.effect));
 	}
 }
 
@@ -2244,11 +2243,7 @@ function each(anchor_node, collection, flags, key_fn, render_fn, fallback_fn, re
 				? []
 				: Array.from(maybe_array);
 			if (key_fn !== null) {
-				const length = array.length;
-				keys = Array(length);
-				for (let i = 0; i < length; i++) {
-					keys[i] = key_fn(array[i]);
-				}
+				keys = array.map(key_fn);
 			}
 			if (fallback_fn !== null) {
 				if (array.length === 0) {
@@ -3163,7 +3158,7 @@ export function mount(component, options) {
 			if (hydration_fragment !== null) {
 				remove(hydration_fragment);
 			}
-			destroy_signal(/** @type {import('./types.js').Signal} */ (block.effect));
+			destroy_signal(/** @type {import('./types.js').EffectSignal} */ (block.effect));
 		}
 	];
 }