A method or accessor with empty body is implicitly abstract.

dart/lib/compiler/implementation/tree/nodes.dart

Index: dart/lib/compiler/implementation/tree/nodes.dart
diff --git a/dart/lib/compiler/implementation/tree/nodes.dart b/dart/lib/compiler/implementation/tree/nodes.dart
index 1c158ed0049c365a9849e2a82fd803c6c33e1353..9d0be9eba2addf75035009ed4cfae6484e06f9ef 100644
--- a/dart/lib/compiler/implementation/tree/nodes.dart
+++ b/dart/lib/compiler/implementation/tree/nodes.dart
@@ -635,12 +635,12 @@ class FunctionExpression extends Expression {
     if (body != null) body.accept(visitor);
   }
 
-  bool hasBody() {
-    // TODO(karlklose,ahe): refactor AST nodes (issue 1713).
-    if (body.asReturn() != null) return true;
-    NodeList statements = body.asBlock().statements;
-    return (!statements.nodes.isEmpty ||
-            !identical(statements.getBeginToken().kind, $SEMICOLON));
+  bool hasBody() => body.asEmptyStatement() == null;
+
+  bool hasEmptyBody() {
+    Block block = body.asBlock();
+    if (block == null) return false;
+    return block.statements.isEmpty;
   }
 
   Token getBeginToken() {