pkg/serialization types cleanup

pkg/serialization/lib/src/serialization_rule.dart

Index: pkg/serialization/lib/src/serialization_rule.dart
diff --git a/pkg/serialization/lib/src/serialization_rule.dart b/pkg/serialization/lib/src/serialization_rule.dart
index d7560b7e274792e97b6c9ad613a272130aaa3044..1a592a7eb8411351d6c402349a772e2393d8f383 100644
--- a/pkg/serialization/lib/src/serialization_rule.dart
+++ b/pkg/serialization/lib/src/serialization_rule.dart
@@ -27,10 +27,10 @@ abstract class SerializationRule {
    * Rules belong uniquely to a particular Serialization instance, and can
    * be identified within it by number.
    */
-  void set number(x) {
-    if (_number != null && _number != x) throw
+  void set number(int value) {
+    if (_number != null && _number != value) throw
         new SerializationException("Rule numbers cannot be changed, once set");
-    _number = x;
+    _number = value;
   }
 
   /**
@@ -91,7 +91,7 @@ abstract class SerializationRule {
    * to see how bad it is.
    */
   // TODO(alanknight): Reconsider whether this should be handled differently.
-  get mustBePrimary => false;
+  bool get mustBePrimary => false;
 
   /**
    * Create the new object corresponding to [state] using the rules