perf: use Set for rest-prop exclude lists in server, legacy, and shared utils

Closes #18601

The client runes `rest_props` path already uses `Set` + `.has()` for O(1)
exclude lookups. Three sibling paths still used arrays + `.includes()`,
giving O(|props| × |exclude|) per operation:

- Server `rest_props` (SSR)
- `exclude_from_object` (rest destructuring, shared)
- `legacy_rest_props` (Svelte 4 compat $$restProps proxy)

This converts all three to accept `Set<string>` and updates the compiler
to emit `new Set([...])` instead of plain arrays, aligning all paths with
the existing client runes behavior.

Tested: snapshot, compiler, runtime-runes, runtime-legacy, signals, ssr,
lint — all pass.

🤖 Generated with Codebuff
Co-Authored-By: Codebuff <noreply@codebuff.com>

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

@@ -450,14 +450,13 @@ export function client_component(analysis, options) {
 		for (const [name, binding] of analysis.instance.scope.declarations) {
 			if (binding.kind === 'bindable_prop') named_props.push(binding.prop_alias ?? name);
 		}
-
 		component_block.body.unshift(
 			b.const(
 				'$$restProps',
 				b.call(
 					'$.legacy_rest_props',
 					b.id('$$sanitized_props'),
-					b.array(named_props.map((name) => b.literal(name)))
+					b.new('Set', b.array(named_props.map((name) => b.literal(name))))
 				)
 			)
 		);
@@ -477,7 +476,7 @@ export function client_component(analysis, options) {
 		component_block.body.unshift(
 			b.const(
 				'$$sanitized_props',
-				b.call('$.legacy_rest_props', b.id('$$props'), b.array(to_remove))
+				b.call('$.legacy_rest_props', b.id('$$props'), b.new('Set', b.array(to_remove)))
 			)
 		);
 	}

packages/svelte/src/compiler/phases/3-transform/server/transform-server.js

@@ -288,14 +288,13 @@ export function server_component(analysis, options) {
 		for (const [name, binding] of analysis.instance.scope.declarations) {
 			if (binding.kind === 'bindable_prop') named_props.push(binding.prop_alias ?? name);
 		}
-
 		component_block.body.unshift(
 			b.const(
 				'$$restProps',
 				b.call(
 					'$.rest_props',
 					b.id('$$sanitized_props'),
-					b.array(named_props.map((name) => b.literal(name)))
+					b.new('Set', b.array(named_props.map((name) => b.literal(name))))
 				)
 			)
 		);

packages/svelte/src/compiler/utils/ast.js

@@ -297,7 +297,11 @@ function _extract_paths(paths, inserts, param, expression, update_expression, ha
 						}
 					}
 
-					const rest_expression = b.call('$.exclude_from_object', expression, b.array(props));
+					const rest_expression = b.call(
+						'$.exclude_from_object',
+						expression,
+						b.new('Set', b.array(props))
+					);
 
 					if (prop.argument.type === 'Identifier') {
 						paths.push({

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

@@ -96,11 +96,11 @@ export function rest_props(props, exclude, name) {
 
 /**
  * The proxy handler for legacy $$restProps and $$props
- * @type {ProxyHandler<{ props: Record<string | symbol, unknown>, exclude: Array<string | symbol>, special: Record<string | symbol, (v?: unknown) => unknown>, version: Source<number>, parent_effect: Effect }>}}
+ * @type {ProxyHandler<{ props: Record<string | symbol, unknown>, exclude: Set<string | symbol>, special: Record<string | symbol, (v?: unknown) => unknown>, version: Source<number>, parent_effect: Effect }>}}
  */
 const legacy_rest_props_handler = {
 	get(target, key) {
-		if (target.exclude.includes(key)) return;
+		if (target.exclude.has(key)) return;
 		get(target.version);
 		return key in target.special ? target.special[key]() : target.props[key];
 	},
@@ -132,7 +132,7 @@ const legacy_rest_props_handler = {
 		return true;
 	},
 	getOwnPropertyDescriptor(target, key) {
-		if (target.exclude.includes(key)) return;
+		if (target.exclude.has(key)) return;
 		if (key in target.props) {
 			return {
 				enumerable: true,
@@ -143,23 +143,23 @@ const legacy_rest_props_handler = {
 	},
 	deleteProperty(target, key) {
 		// Svelte 4 allowed for deletions on $$restProps
-		if (target.exclude.includes(key)) return true;
+		if (target.exclude.has(key)) return true;
-		target.exclude.push(key);
+		target.exclude.add(key);
 		update(target.version);
 		return true;
 	},
 	has(target, key) {
-		if (target.exclude.includes(key)) return false;
+		if (target.exclude.has(key)) return false;
 		return key in target.props;
 	},
 	ownKeys(target) {
-		return Reflect.ownKeys(target.props).filter((key) => !target.exclude.includes(key));
+		return Reflect.ownKeys(target.props).filter((key) => !target.exclude.has(key));
 	}
 };
 
 /**
  * @param {Record<string, unknown>} props
- * @param {string[]} exclude
+ * @param {Set<string>} exclude
  * @returns {Record<string, unknown>}
  */
 export function legacy_rest_props(props, exclude) {

packages/svelte/src/internal/server/index.js

@@ -343,7 +343,7 @@ export function slot(renderer, $$props, name, slot_props, fallback_fn) {
 
 /**
  * @param {Record<string, unknown>} props
- * @param {string[]} rest
+ * @param {Set<string>} rest
  * @returns {Record<string, unknown>}
  */
 export function rest_props(props, rest) {
@@ -351,7 +351,7 @@ export function rest_props(props, rest) {
 	const rest_props = {};
 	let key;
 	for (key of Object.keys(props)) {
-		if (!rest.includes(key)) {
+		if (!rest.has(key)) {
 			rest_props[key] = props[key];
 		}
 	}

packages/svelte/src/internal/shared/utils.js

@@ -121,7 +121,7 @@ export function to_array(value, n) {
 
 /**
  * @param {Record<string | symbol, unknown>} obj
- * @param {Array<string | symbol>} keys
+ * @param {Set<string | symbol>} keys
  * @returns {Record<string | symbol, unknown>}
  */
 export function exclude_from_object(obj, keys) {
@@ -129,13 +129,13 @@ export function exclude_from_object(obj, keys) {
 	var result = {};
 
 	for (var key in obj) {
-		if (!keys.includes(key)) {
+		if (!keys.has(key)) {
 			result[key] = obj[key];
 		}
 	}
 
 	for (var symbol of Object.getOwnPropertySymbols(obj)) {
-		if (Object.propertyIsEnumerable.call(obj, symbol) && !keys.includes(symbol)) {
+		if (Object.propertyIsEnumerable.call(obj, symbol) && !keys.has(symbol)) {
 			result[symbol] = obj[symbol];
 		}
 	}