Introduce _emitParameterReferences to avoid mixing params with param references.

test/codegen/destructuring.dart

+import 'dart-ext:foo';
+import 'package:js/src/varargs.dart';
+
 f(int a, b, [c = 1]) {
   f(a, b, c);
 }
+external f_ext(int a, b, [c = 1]);
+f_nat(int a, b, [c = 1]) native "f_nat";
+f_sync(int a, b, [c = 1]) sync* {}
+f_async(int a, b, [c = 1]) async* {}
+
 g(int a, b, {c : 1}) {
   f(a, b, c);
 }
+external g_ext(int a, b, {c : 1});
+g_nat(int a, b, {c : 1}) native "g_nat";
+g_sync(int a, b, {c : 1}) sync* {}
+g_async(int a, b, {c : 1}) async* {}
+
+r(int a, @rest others) {
+  r(a, spread(others));
+}
+external r_ext(int a, @rest others);
+r_nat(int a, @rest others) native "r_nat";
+r_sync(int a, @rest others) sync* {}
+r_async(int a, @rest others) async* {}
 
 invalid_names1(int let, function, arguments) {
   f(let, function, arguments);
 }
 invalid_names2([int let, function = 1, arguments]) {
   f(let, function, arguments);
 }
 invalid_names3({int let, function, arguments : 2}) {
   f(let, function, arguments);
 }
 
 names_clashing_with_object_props({int constructor, valueOf, hasOwnProperty : 2}) {
   f(constructor, valueOf, hasOwnProperty);
 }