Fasta kernel AST builder.

pkg/fasta/lib/src/kernel/redirecting_factory_body.dart

Index: pkg/fasta/lib/src/kernel/redirecting_factory_body.dart
diff --git a/pkg/fasta/lib/src/kernel/redirecting_factory_body.dart b/pkg/fasta/lib/src/kernel/redirecting_factory_body.dart
new file mode 100644
index 0000000000000000000000000000000000000000..ada143602d77deff9a5fae07d68525d1e942fdb1
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+++ b/pkg/fasta/lib/src/kernel/redirecting_factory_body.dart
@@ -0,0 +1,45 @@
+// Copyright (c) 2016, 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.
+
+library fasta.redirecting_factory_body;
+
+import 'package:kernel/ast.dart' show
+    InvalidStatement,
+    Member,
+    Procedure;
+
+class RedirectingFactoryBody extends InvalidStatement {
+  final Member target;
+
+  RedirectingFactoryBody(this.target);
+}
+
+bool isRedirectingFactory(Member member) {
+  return member is Procedure &&
+      member.function.body is RedirectingFactoryBody;
+}
+
+Member getImmediateRedirectionTarget(Member member) {
+  if (isRedirectingFactory(member)) {
+    Procedure procedure = member;
+    RedirectingFactoryBody body = procedure.function.body;
+    return body.target;
+  } else {
+    return null;
+  }
+}
+
+Member getRedirectionTarget(Procedure member) {
+  // We use the [tortoise and hare algorithm]
+  // (https://en.wikipedia.org/wiki/Cycle_detection#Tortoise_and_hare) to
+  // handle cycles.
+  Member tortoise = member;
+  Member hare = getImmediateRedirectionTarget(member);
+  while (tortoise != hare) {
+    if (!isRedirectingFactory(tortoise)) return tortoise;
+    tortoise = getImmediateRedirectionTarget(tortoise);
+    hare = getImmediateRedirectionTarget(getImmediateRedirectionTarget(hare));
+  }
+  return null;
+}