Fix some array function parsing and serialization issues

Quite similar to #256 and also uses its test, but also fixes the serializer and doesn't try to parse an untyped 'x => x'.

src/ast.ts

@@ -117,7 +117,8 @@ export function nodeIsCallable(kind: NodeKind): bool {
     case NodeKind.IDENTIFIER:
     case NodeKind.CALL:
     case NodeKind.ELEMENTACCESS:
-    case NodeKind.PROPERTYACCESS: return true;
+    case NodeKind.PROPERTYACCESS:
+    case NodeKind.PARENTHESIZED: return true;
   }
   return false;
 }