look, ok, it did work, i just needed to update the snapshots

packages/svelte/tests/parser-modern/samples/snippets/output.json

@@ -25,6 +25,9 @@
 					"name": "foo"
 				},
 				"context": {
+					"type": "ArrayPattern",
+					"elements": [
+						{
 							"type": "Identifier",
 							"name": "msg",
 							"start": 43,
@@ -44,6 +47,8 @@
 									}
 								}
 							}
+						}
+					]
 				},
 				"body": {
 					"type": "Fragment",
@@ -127,7 +132,8 @@
 					},
 					"name": "foo"
 				},
-				"argument": {
+				"arguments": [
+					{
 						"type": "Identifier",
 						"start": 96,
 						"end": 99,
@@ -143,6 +149,7 @@
 						},
 						"name": "msg"
 					}
+				]
 			}
 		],
 		"transparent": false