Support redirecting factory constructors in the VM (issue 3969).

tests/language/factory_redirection_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.
+
+class A<T> {
+  A() : x = null;
+
+  const A.constant(T x) : this.x = x;

[siva, 2012/09/24 20:51:35]

const A.constant(this.x); ?

[regis, 2012/09/24 21:41:28]

Done.

+
+  factory A.factory() {
+    return new B<Set>();
+  }
+
+  final T x;
+}
+
+class B<T> extends A<T> {
+  B();
+
+  factory B.A() = A<T>;
+
+  const factory B.A_constant(T x) = A<T>.constant;
+
+  factory B.A_factory() = A<T>.factory;
+}
+
+class C<K, V> extends B<V> {
+  C();
+
+  factory C.A() = A<V>;
+
+  factory C.A_factory() = A<V>.factory;

[siva, 2012/09/24 20:51:35]

Would it be legal here to redirect to A<K>.factory; ?

[regis, 2012/09/24 21:41:28]

Yes, it would. But you would need to call new C<bool, ...> for the test to work.
Actually, I tried and ran into another issue, which I will fix: type arguments
of canonical types should be allocated in the old space, but they are not
always.

+
+  const factory C.B_constant(V x) = B<V>.A_constant;
+}
+
+main() {
+  Expect.isTrue(new A<List>() is A<List>);
+  Expect.isTrue(new A<bool>.constant(true).x);
+  Expect.isTrue(new A<List>.factory() is B<Set>);
+  Expect.isTrue(new B<List>.A() is A<List>);
+  Expect.isTrue(new B<bool>.A_constant(true).x);
+  Expect.isTrue(new B<List>.A_factory() is B<Set>);
+  Expect.isTrue(new C<String, num>.A() is A<num>);
+  Expect.isTrue(new C<String, num>.A_factory() is B<Set>);
+  Expect.isTrue(new C<String, bool>.B_constant(true).x);
+}