Introduce _emitParameterReferences to avoid mixing params with param references.

test/codegen/destructuring.dart

Index: test/codegen/destructuring.dart
diff --git a/test/codegen/destructuring.dart b/test/codegen/destructuring.dart
index a0912437ed357d714d59eaf3e44dedda0ccb4567..51bf057fd81d4924e467894e6ded28d3f190e144 100644
--- a/test/codegen/destructuring.dart
+++ b/test/codegen/destructuring.dart
@@ -1,9 +1,29 @@
+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);