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diff --git a/src/main/java/com/google/devtools/build/lib/collect/nestedset/NaiveLinkOrderExpander.java b/src/main/java/com/google/devtools/build/lib/collect/nestedset/NaiveLinkOrderExpander.java
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+// Copyright 2014 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.devtools.build.lib.collect.nestedset;
+
+import com.google.common.collect.ImmutableCollection;
+
+/**
+ * A nested set expander that implements naive left-to-right preordering.
+ *
+ * <p>For example, for the nested set {B, D, {A, C}}, the iteration order is "B D A C".
+ *
+ * <p>This implementation is intended for backwards-compatible nested set replacements of code that
+ * uses naive preordering.
+ *
+ * <p>The implementation is called naive because it does no special treatment of dependency graphs
+ * that are not trees. For such graphs the property of parent-before-dependencies in the iteration
+ * order will not be upheld. For example, the diamond-shape graph A->{B, C}, B->{D}, C->{D} will be
+ * enumerated as "A B D C" rather than "A B C D" or "A C B D".
+ *
+ * <p>The difference from {@link LinkOrderNestedSet} is that this implementation gives priority to
+ * left-to-right order over dependencies-after-parent ordering. Note that the latter is usually more
+ * important, so please use {@link LinkOrderNestedSet} whenever possible.
+ */
+final class NaiveLinkOrderExpander<E> implements NestedSetExpander<E> {
+
+  @SuppressWarnings("unchecked")
+  @Override
+  public void expandInto(NestedSet<E> set, Uniqueifier uniqueifier,
+      ImmutableCollection.Builder<E> builder) {
+
+    for (Object e : set.directMembers()) {
+      if (uniqueifier.isUnique(e)) {
+        builder.add((E) e);
+      }
+    }
+
+    for (NestedSet<E> subset : set.transitiveSets()) {
+      if (!subset.isEmpty() && uniqueifier.isUnique(subset)) {
+        expandInto(subset, uniqueifier, builder);
+      }
+    }
+  }
+}