package:observe fix various api issues

pkg/observe/lib/src/change_record.dart

Index: pkg/observe/lib/src/change_record.dart
diff --git a/pkg/observe/lib/src/change_record.dart b/pkg/observe/lib/src/change_record.dart
index 99e806ddb373b56d528f884d74be91dd7413badc..bb584e8f427aa2e35f0e9dc612a774094e0c21c8 100644
--- a/pkg/observe/lib/src/change_record.dart
+++ b/pkg/observe/lib/src/change_record.dart
@@ -5,22 +5,41 @@
 part of observe;
 
 /** Records a change to an [Observable]. */
-abstract class ChangeRecord {
-  // TODO(jmesserly): rename this--it's confusing. Perhaps "matches"?
-  /** True if the change affected the given item, otherwise false. */
-  bool changes(key);
-}
+// TODO(jmesserly): remove this type
+abstract class ChangeRecord {}
 
 /** A change record to a field of an observable object. */
-class PropertyChangeRecord extends ChangeRecord {
-  /** The field that was changed. */
-  final Symbol field;
+class PropertyChangeRecord<T> extends ChangeRecord {
+  /**
+   * *Deprecated* use [name] instead.
+   * The field that was changed.
+   */
+  @deprecated
+  Symbol get field => name;
+
+  /** The object that changed. */
+  final object;
+
+  /** The name of the property that changed. */
+  final Symbol name;
 
-  PropertyChangeRecord(this.field);
+  /** The previous value of the property. */
+  final T oldValue;
 
-  bool changes(key) => key is Symbol && field == key;
+  /** The new value of the property. */
+  final T newValue;
 
-  String toString() => '#<PropertyChangeRecord $field>';
+  PropertyChangeRecord(this.object, this.name, this.oldValue, this.newValue);
+
+  /*
+   * *Deprecated* instead of `record.changes(key)` simply do
+   * `key == record.name`.
+   */
+  @deprecated
+  bool changes(key) => key is Symbol && name == key;
+
+  String toString() =>
+      '#<PropertyChangeRecord $name from: $oldValue to: $newValue>';
 }
 
 /** A change record for an observable list. */
@@ -41,16 +60,23 @@ class ListChangeRecord extends ChangeRecord {
     }
   }
 
+  /**
+   * *Deprecated* use [indexChanged] instead.
+   * Returns true if the provided index was changed by this operation.
+   */
+  @deprecated
+  bool changes(value) => indexChanged(value);
+
   /** Returns true if the provided index was changed by this operation. */
-  bool changes(key) {
+  bool indexChanged(otherIndex) {
     // If key isn't an int, or before the index, then it wasn't changed.
-    if (key is! int || key < index) return false;
+    if (otherIndex is! int || otherIndex < index) return false;
 
     // If this was a shift operation, anything after index is changed.
     if (addedCount != removedCount) return true;
 
     // Otherwise, anything in the update range was changed.
-    return key < index + addedCount;
+    return otherIndex < index + addedCount;
   }
 
   String toString() => '#<ListChangeRecord index: $index, '