Fix await transformation of function calls

tests/language/await_regression_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 
 
 import 'dart:async';
 import 'package:expect/expect.dart';
 
 later(vodka) => new Future.value(vodka);
@@ skipping 12 matching lines @@
 addLater({a, b}) => new Future.value(a + b);
 
 // Regression test for issue 21480.
 testNamedArguments() async {
   var sum = await addLater(a:5, b:10);
   Expect.equals(sum, 15);
   sum = await addLater(b:11, a:-11);
   Expect.equals(sum, 0);
 }
 
+testSideEffects() async {
+  Future foo(int a1, int a2) {
+    Expect.equals(10, a1);
+    Expect.equals(11, a2);
+    return new Future.value();
+  }
+  int a = 10;
+  await foo(a++, a++);
+  Expect.equals(12, a);
+}
+
 main() async {
   testNestedFunctions();
   testNamedArguments();
+  testSideEffects();
 }