A method or accessor with empty body is implicitly abstract.

dart/tests/compiler/dart2js/patch_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import "../../../lib/compiler/implementation/dart2jslib.dart";
 import "../../../lib/compiler/implementation/elements/elements.dart";
 import "../../../lib/compiler/implementation/tree/tree.dart";
 import "../../../lib/compiler/implementation/util/util.dart";
 import "mock_compiler.dart";
 import "parser_helper.dart";
@@ skipping 16 matching lines @@
     Expect.isNotNull(node.body);
     // If the element has a body it is either a Block or a Return statement,
     // both with different begin and end tokens.
     Expect.isTrue(node.body is Block || node.body is Return);
     Expect.notEquals(node.body.getBeginToken(), node.body.getEndToken());
 }
 
 void expectHasNoBody(compiler, Element element) {
     var node = element.parseNode(compiler);
     Expect.isNotNull(node, "Element isn't parseable, when a body was expected");
-    Expect.isNotNull(node.body);
-    // If the element has no body it is a Block with identical begin and end
-    // tokens (the semicolon).
-    Expect.isTrue(node.body is Block);
-    Expect.identical(node.body.getBeginToken(), node.body.getEndToken());
+    Expect.isFalse(node.hasBody());
 }
 
 Element ensure(compiler,
                String name,
                Element lookup(name),
                {bool isPatched: false,
                 bool isPatch: false,
                 bool isMethod: true,
                 bool isGetter: false,
                 bool isFound: true}) {
@@ skipping 309 matching lines @@
 
 main() {
   testPatchFunction();
   testPatchMember();
   testPatchGetter();
   testRegularMember();
   testGhostMember();
   testInjectFunction();
   testPatchSignatureCheck();
 }