fix: ensure generate guards against keywords (#9790)

* fix: ensure generate guards against keywords

* changeset

* lint

* Update .changeset/old-flies-jog.md

---------

Co-authored-by: Rich Harris <richard.a.harris@gmail.com>

.changeset/old-flies-jog.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: ensure generated code does not use keywords as variable names

packages/svelte/src/compiler/phases/constants.js

@@ -196,3 +196,43 @@ export const EventModifiers = [
 	'self',
 	'trusted'
 ];
+
+export const JsKeywords = [
+	'class',
+	'break',
+	'const',
+	'let',
+	'var',
+	'continue',
+	'if',
+	'for',
+	'while',
+	'do',
+	'new',
+	'static',
+	'true',
+	'false',
+	'void',
+	'with',
+	'yield',
+	'await',
+	'typeof',
+	'throw',
+	'throws',
+	'null',
+	'delete',
+	'default',
+	'catch',
+	'debugger',
+	'case',
+	'arguments',
+	'else',
+	'extends',
+	'export',
+	'import',
+	'extends',
+	'switch',
+	'instanceof',
+	'return',
+	'this'
+];

packages/svelte/src/compiler/phases/scope.js

@@ -4,7 +4,7 @@ import { is_element_node } from './nodes.js';
 import * as b from '../utils/builders.js';
 import { error } from '../errors.js';
 import { extract_identifiers, extract_identifiers_from_expression } from '../utils/ast.js';
-import { Runes } from './constants.js';
+import { JsKeywords, Runes } from './constants.js';
 
 export class Scope {
 	/** @type {ScopeRoot} */
@@ -133,7 +133,8 @@ export class Scope {
 		while (
 			this.references.has(name) ||
 			this.declarations.has(name) ||
-			this.root.conflicts.has(name)
+			this.root.conflicts.has(name) ||
+			JsKeywords.includes(name)
 		) {
 			name = `${preferred_name}_${n++}`;
 		}