Native abstract classes may be 'instantiated'

tests/compiler/dart2js_native/abstract_class_test.dart

+// Copyright (c) 2013, 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 "package:expect/expect.dart";
+
+// Native classes can have subclasses that are not declared to the program.  The
+// subclasses are indistinguishable from the base class.  This means that
+// abstract native classes can appear to have instances.
+
+abstract class A native "A" {
+}
+
+abstract class B native "B" {
+  foo() native;
+}
+
+class C {}
+
+makeA() native;
+makeB() native;
+
+void setup() native """
+// This code is all inside 'setup' and so not accesible from the global scope.
+function A(){}
+function B(){}
+B.prototype.foo = function() { return 'B.foo'; };
+makeA = function(){return new A};
+makeB = function(){return new B};
+""";
+
+var inscrutable;
+main() {
+  setup();
+  inscrutable = (x) => x;
+  inscrutable = inscrutable(inscrutable);
+
+  var a = makeA();
+  var b = makeB();
+  var c = inscrutable(new C());
+
+  Expect.isTrue(a is A);
+  Expect.isFalse(b is A);
+  Expect.isFalse(c is A);
+
+  Expect.isFalse(a is B);
+  Expect.isTrue(b is B);
+  Expect.isFalse(c is B);
+
+  Expect.isFalse(a is C);
+  Expect.isFalse(b is C);
+  Expect.isTrue(c is C);
+
+  Expect.equals('B.foo', b.foo());
+}