Check for cyclic reference in typedefs

sdk/lib/_internal/compiler/implementation/warnings.dart

Index: sdk/lib/_internal/compiler/implementation/warnings.dart
diff --git a/sdk/lib/_internal/compiler/implementation/warnings.dart b/sdk/lib/_internal/compiler/implementation/warnings.dart
index 2e377a430539d2c386f6299cee4e2f92f668df49..fcadc1227a67a69bc6449fff887832da82b65d3c 100644
--- a/sdk/lib/_internal/compiler/implementation/warnings.dart
+++ b/sdk/lib/_internal/compiler/implementation/warnings.dart
@@ -193,6 +193,16 @@ class MessageKind {
   static const CYCLIC_TYPE_VARIABLE = const MessageKind(
       "cyclic reference to type variable #{typeVariableName}");
 
+  static const CYCLIC_TYPEDEF = const MessageKind(
+      "typedef #{typedefName} refers to itself");
+
+  static const CYCLIC_TYPEDEF_ONE = const MessageKind(
+      "typedef #{typedefName} refers to itself through "
+      "typedef #{otherTypedefName}");
+
+  static const CYCLIC_TYPEDEF_MORE = const MessageKind(
+      "typedef #{typedefName} refers to itself through several typedefs");
+
   static const CLASS_NAME_EXPECTED = const MessageKind(
       "class name expected");