Add regression tests from Luke's bug reports. Part 1.

pkg/front_end/testcases/regress/issue_29983.dart.dartk.expect

Index: pkg/front_end/testcases/regress/issue_29983.dart.dartk.expect
diff --git a/pkg/front_end/testcases/regress/issue_29983.dart.dartk.expect b/pkg/front_end/testcases/regress/issue_29983.dart.dartk.expect
new file mode 100644
index 0000000000000000000000000000000000000000..d20670ca934690a589c5aa155f3b03368eba411c
--- /dev/null
+++ b/pkg/front_end/testcases/regress/issue_29983.dart.dartk.expect
@@ -0,0 +1,9 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+const field dynamic #errors = const <dynamic>["pkg/front_end/testcases/regress/issue_29983.dart:6:10: Error: 'sync*' and 'async*' can't return a value.\n  return missing;\n         ^"]/* from null */;
+static method f() → dynamic {
+  return throw new core::NoSuchMethodError::•(null, #missing, <dynamic>[], <dynamic, dynamic>{}, null);
+}
+static method main() → dynamic {}