Using 'interface' and 'abstract' for methods should produce error

pkg/unittest/interfaces.dart

Index: pkg/unittest/interfaces.dart
diff --git a/pkg/unittest/interfaces.dart b/pkg/unittest/interfaces.dart
index 9a5d7fbac2d92b2934befae4c4318e548e2d2a86..42c498bdfd26ffb5b33e59367a18bf68db24d8f2 100644
--- a/pkg/unittest/interfaces.dart
+++ b/pkg/unittest/interfaces.dart
@@ -28,19 +28,19 @@ typedef String ErrorFormatter(actual, Matcher matcher, String reason,
  */
 abstract class Description {
   /** Change the value of the description. */
-  abstract Description replace(String text);
+  Description replace(String text);
 
   /** This is used to add arbitrary text to the description. */
-  abstract Description add(String text);
+  Description add(String text);
 
   /** This is used to add a meaningful description of a value. */
-  abstract Description addDescriptionOf(value);
+  Description addDescriptionOf(value);
 
   /**
    * This is used to add a description of an [Iterable] [list],
    * with appropriate [start] and [end] markers and inter-element [separator].
    */
-  abstract Description addAll(String start, String separator, String end,
+  Description addAll(String start, String separator, String end,
                      Iterable list);
 }
 
@@ -59,10 +59,10 @@ abstract class Matcher {
    * and may be used to add details about the mismatch that are too
    * costly to determine in [describeMismatch].
    */
-  abstract bool matches(item, MatchState matchState);
+  bool matches(item, MatchState matchState);
 
   /** This builds a textual description of the matcher. */
-  abstract Description describe(Description description);
+  Description describe(Description description);
 
   /**
    * This builds a textual description of a specific mismatch. [item]
@@ -74,7 +74,7 @@ abstract class Matcher {
    * information that is not typically included but can be of help in
    * diagnosing failures, such as stack traces.
    */
-  abstract Description describeMismatch(item, Description mismatchDescription,
+  Description describeMismatch(item, Description mismatchDescription,
       MatchState matchState, bool verbose);
 }
 
@@ -86,7 +86,7 @@ abstract class Matcher {
  */
 abstract class FailureHandler {
   /** This handles failures given a textual decription */
-  abstract void fail(String reason);
+  void fail(String reason);
 
   /**
    * This handles failures given the actual [value], the [matcher]
@@ -96,7 +96,7 @@ abstract class FailureHandler {
    * these to create a detailed error message (typically by calling
    * an [ErrorFormatter]) and then call [fail] with this message.
    */
-  abstract void failMatch(actual, Matcher matcher, String reason,
+  void failMatch(actual, Matcher matcher, String reason,
                  MatchState matchState, bool verbose);
 }