--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/truffle/com.oracle.truffle.api/src/com/oracle/truffle/api/Assumption.java	Wed Jun 17 10:58:08 2015 +0200
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2012, 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 com.oracle.truffle.api;
+
+import com.oracle.truffle.api.nodes.*;
+
+/**
+ * An assumption is a global boolean flag that starts with the value true (i.e., the assumption is
+ * valid) and can subsequently be invalidated (using {@link Assumption#invalidate()}). Once
+ * invalidated, an assumption can never get valid again. Assumptions can be created using the
+ * {@link TruffleRuntime#createAssumption()} or the {@link TruffleRuntime#createAssumption(String)}
+ * method. The Truffle compiler has special knowledge of this class in order to produce efficient
+ * machine code for checking an assumption in case the assumption object is a compile time constant.
+ * Therefore, assumptions should be stored in final fields in Truffle nodes.
+ *
+ * All instances of classes implementing {@code Assumption} must be held in {@code final} fields for
+ * compiler optimizations to take effect.
+ */
+public interface Assumption {
+
+    /**
+     * Checks that this assumption is still valid. The method throws an exception, if this is no
+     * longer the case. This method is preferred over the {@link #isValid()} method when writing
+     * guest language interpreter code. The catch block should perform a node rewrite (see
+     * {@link Node#replace(Node)}) with a node that no longer relies on the assumption.
+     *
+     * @throws InvalidAssumptionException If the assumption is no longer valid.
+     */
+    void check() throws InvalidAssumptionException;
+
+    /**
+     * Checks whether the assumption is still valid.
+     *
+     * @return a boolean value indicating the validity of the assumption
+     */
+    boolean isValid();
+
+    /**
+     * Invalidates this assumption. Performs no operation, if the assumption is already invalid.
+     */
+    void invalidate();
+
+    /**
+     * A name for the assumption that is used for debug output.
+     *
+     * @return the name of the assumption
+     */
+    String getName();
+}