fix validation (we were mutating the wrong array)

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

@@ -9,12 +9,6 @@ import * as b from '#compiler/builders';
  * @param {ComponentContext} context
  */
 export function SnippetBlock(node, context) {
-	const body = /** @type {BlockStatement} */ (context.visit(node.body));
-
-	if (dev) {
-		body.body.unshift(b.stmt(b.call('$.validate_snippet_args', b.id('$$payload'))));
-	}
-
 	let fn = b.function_declaration(
 		node.expression,
 		[b.id('$$payload'), ...node.parameters],
@@ -27,6 +21,7 @@ export function SnippetBlock(node, context) {
 	const push_to = node.metadata.can_hoist ? context.state.hoisted : context.state.init;
 
 	if (dev) {
+		fn.body.body.unshift(b.stmt(b.call('$.validate_snippet_args', b.id('$$payload'))));
 		push_to.push(b.stmt(b.call('$.prevent_snippet_stringification', fn.id)));
 	}
 

packages/svelte/tests/runtime-runes/samples/snippet-invalid-call/_config.js

@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true
+	},
+
+	error: 'invalid_snippet_arguments'
+});

packages/svelte/tests/runtime-runes/samples/snippet-invalid-call/main.svelte

@@ -0,0 +1,7 @@
+<script>
+	test();
+</script>
+
+{#snippet test()}
+	<p>hello</p>
+{/snippet}