initial sync*, part of #221

test/codegen/expect/syncstar_yield_test.txt

Index: test/codegen/expect/syncstar_yield_test.txt
diff --git a/test/codegen/expect/syncstar_yield_test.txt b/test/codegen/expect/syncstar_yield_test.txt
new file mode 100644
index 0000000000000000000000000000000000000000..20e289e3afb00888d95238dcbb1b85eb2fd51528
--- /dev/null
+++ b/test/codegen/expect/syncstar_yield_test.txt
@@ -0,0 +1,13 @@
+// Messages from compiling syncstar_yield_test.dart
+info: line 97, column 51 of test/codegen/expect.dart: [DynamicCast] expected (dynamic) will need runtime check to cast to type String
+      String stringDifference = _stringDifference(expected, actual);
+                                                  ^^^^^^^^
+info: line 97, column 61 of test/codegen/expect.dart: [DynamicCast] actual (dynamic) will need runtime check to cast to type String
+      String stringDifference = _stringDifference(expected, actual);
+                                                            ^^^^^^
+info: line 372, column 14 of test/codegen/expect.dart: [DynamicInvoke] check(e) requires dynamic invoke
+        if (!check(e)) {
+             ^^^^^^^^
+info: line 17, column 28 of test/codegen/syncstar_yield_test.dart: [DynamicCast] p (dynamic) will need runtime check to cast to type num
+    a: for (int i = 0; i < p; i++) {
+                           ^