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diff --git a/src/jdk/nashorn/internal/ir/OptimisticLexicalContext.java b/src/jdk/nashorn/internal/ir/OptimisticLexicalContext.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;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Deque;
+import java.util.List;
+import jdk.nashorn.internal.codegen.types.Type;
+
+/**
+ * Lexical context that keeps track of optimistic assumptions (if any)
+ * made during code generation. Used from Attr and FinalizeTypes
+ */
+public class OptimisticLexicalContext extends LexicalContext {
+
+    private final boolean isEnabled;
+
+    class Assumption {
+        Symbol symbol;
+        Type   type;
+
+        Assumption(final Symbol symbol, final Type type) {
+            this.symbol = symbol;
+            this.type   = type;
+        }
+        @Override
+        public String toString() {
+            return symbol.getName() + "=" + type;
+        }
+    }
+
+    /** Optimistic assumptions that could be made per function */
+    private final Deque<List<Assumption>> optimisticAssumptions = new ArrayDeque<>();
+
+    /**
+     * Constructor
+     * @param isEnabled are optimistic types enabled?
+     */
+    public OptimisticLexicalContext(final boolean isEnabled) {
+        super();
+        this.isEnabled = isEnabled;
+    }
+
+    /**
+     * Are optimistic types enabled
+     * @return true if optimistic types
+     */
+    public boolean isEnabled() {
+        return isEnabled;
+    }
+
+    /**
+     * Log an optimistic assumption during codegen
+     * TODO : different parameters and more info about the assumption for future profiling
+     * needs
+     * @param symbol symbol
+     * @param type   type
+     */
+    public void logOptimisticAssumption(final Symbol symbol, final Type type) {
+        if (isEnabled) {
+            final List<Assumption> peek = optimisticAssumptions.peek();
+            peek.add(new Assumption(symbol, type));
+        }
+    }
+
+    /**
+     * Get the list of optimistic assumptions made
+     * @return optimistic assumptions
+     */
+    public List<Assumption> getOptimisticAssumptions() {
+        return Collections.unmodifiableList(optimisticAssumptions.peek());
+    }
+
+    /**
+     * Does this method have optimistic assumptions made during codegen?
+     * @return true if optimistic assumptions were made
+     */
+    public boolean hasOptimisticAssumptions() {
+        return !optimisticAssumptions.isEmpty() && !getOptimisticAssumptions().isEmpty();
+    }
+
+    @Override
+    public <T extends LexicalContextNode> T push(final T node) {
+        if (isEnabled) {
+            if(node instanceof FunctionNode) {
+                optimisticAssumptions.push(new ArrayList<Assumption>());
+            }
+        }
+
+        return super.push(node);
+    }
+
+    @Override
+    public <T extends LexicalContextNode> T pop(final T node) {
+        final T popped = super.pop(node);
+        if (isEnabled) {
+            if(node instanceof FunctionNode) {
+                optimisticAssumptions.pop();
+            }
+        }
+        return popped;
+    }
+
+}