breaking: prevent usage of arguments keyword in certain places (#12191)

* breaking: prevent usage of arguments keyword in certain places

* build

* build

* Update packages/svelte/messages/compile-errors/script.md

Co-authored-by: Rich Harris <rich.harris@vercel.com>

* build

* build

* lint

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

.changeset/healthy-zebras-accept.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+breaking: prevent usage of arguments keyword in certain places

packages/svelte/messages/compile-errors/script.md

@@ -50,6 +50,10 @@
 
 > Imports of `svelte/internal/*` are forbidden. It contains private runtime code which is subject to change without notice. If you're importing from `svelte/internal/*` to work around a limitation of Svelte, please open an issue at https://github.com/sveltejs/svelte and explain your use case
 
+## invalid_arguments_usage
+
+> The arguments keyword cannot be used within the template or at the top level of a component
+
 ## legacy_export_invalid
 
 > Cannot use `export let` in runes mode — use `$props()` instead

packages/svelte/src/compiler/errors.js

@@ -213,6 +213,15 @@ export function import_svelte_internal_forbidden(node) {
 	e(node, "import_svelte_internal_forbidden", "Imports of `svelte/internal/*` are forbidden. It contains private runtime code which is subject to change without notice. If you're importing from `svelte/internal/*` to work around a limitation of Svelte, please open an issue at https://github.com/sveltejs/svelte and explain your use case");
 }
 
+/**
+ * The arguments keyword cannot be used within the template or at the top level of a component
+ * @param {null | number | NodeLike} node
+ * @returns {never}
+ */
+export function invalid_arguments_usage(node) {
+	e(node, "invalid_arguments_usage", "The arguments keyword cannot be used within the template or at the top level of a component");
+}
+
 /**
  * Cannot use `export let` in runes mode — use `$props()` instead
  * @param {null | number | NodeLike} node

packages/svelte/src/compiler/phases/2-analyze/index.js

@@ -1238,6 +1238,14 @@ const common_visitors = {
 			return;
 		}
 
+		// If we are using arguments outside of a function, then throw an error
+		if (
+			node.name === 'arguments' &&
+			context.path.every((n) => n.type !== 'FunctionDeclaration' && n.type !== 'FunctionExpression')
+		) {
+			e.invalid_arguments_usage(node);
+		}
+
 		const binding = context.state.scope.get(node.name);
 
 		// if no binding, means some global variable

packages/svelte/tests/compiler-errors/samples/invalid-arguments-usage/_config.js

@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'invalid_arguments_usage',
+		message:
+			'The arguments keyword cannot be used within the template or at the top level of a component'
+	}
+});

packages/svelte/tests/compiler-errors/samples/invalid-arguments-usage/main.svelte

@@ -0,0 +1,3 @@
+<script>
+	arguments
+</script>