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diff --git a/src/jdk/nashorn/internal/ir/JoinPredecessor.java b/src/jdk/nashorn/internal/ir/JoinPredecessor.java
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+/*
+ * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package jdk.nashorn.internal.ir;
+
+/**
+ * Interface implemented by AST nodes that either can occur as predecessors of a control flow join, or contain a control
+ * flow join themselves. JoinPredecessor only provides a getter and setter for a {@link LocalVariableConversion}; the
+ * semantics of control flow for a particular node implementing the interface are shared between
+ * {@code LocalVariableTypesCalculator} that creates the conversions, and {@code CodeGenerator} that uses them.
+ */
+public interface JoinPredecessor {
+    /**
+     * Set the local variable conversions needed to unify their types at a control flow join point.
+     * @param lc the current lexical context
+     * @param conversion the conversions.
+     * @return this node or a different node representing the change.
+     */
+    public JoinPredecessor setLocalVariableConversion(LexicalContext lc, LocalVariableConversion conversion);
+
+    /**
+     * Returns the local variable conversions needed to unify their types at a control flow join point.
+     * @return the local variable conversions needed to unify their types at a control flow join point. Can be null.
+     * Can contain {@link LocalVariableConversion#isLive() dead conversions}.
+     */
+    public LocalVariableConversion getLocalVariableConversion();
+}