Handle int/double case expression types correctly.

tests/language/switch_int_double_test.dart

+// Copyright (c) 2013, 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.
+
+// Test that double literals with no fractional part is not treated as having
+// static type int.
+
+import "package:expect/expect.dart";
+
+void main() {
+  Expect.equals(100, test(1.0));
+  Expect.equals(75, test(0.75));
+  Expect.equals(null, test(0.5));
+}
+
+int test(num ratio) {
+  switch (ratio) {
+    case 0.75:
+      return 75;
+    case 1.0:
+      return 100;
+    case 2:       /// 01: compile-time error
+      return 200; /// 01: continued
+    case 'foo':   /// 02: compile-time error
+      return 400; /// 02: continued
+  }
+}