Allow assignment expressions in conditional expressions

tests/language/src/CondExprTest.dart

Index: tests/language/src/CondExprTest.dart
===================================================================
--- tests/language/src/CondExprTest.dart	(revision 0)
+++ tests/language/src/CondExprTest.dart	(revision 0)
@@ -0,0 +1,25 @@
+// Copyright (c) 2011, 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.
+// Check that conditional expressions can contain assignment expressions.
+
+
+var e1, e2;
+
+f(a) => a < 0 ? e1 = -1 : e2 = 1;
+
+main() {
+  e1 = 0;
+  e2 = 0;
+  var r = f(-100);
+  Expect.equals(-1, r);
+  Expect.equals(-1, e1);
+  Expect.equals(0, e2);
+
+  e1 = 0;
+  e2 = 0;
+  r = f(100);
+  Expect.equals(1, r);
+  Expect.equals(0, e1);
+  Expect.equals(1, e2);
+}