--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/instrument/ProbeFailure.java	Tue Jan 27 20:24:54 2015 -0800
@@ -0,0 +1,145 @@
+/*
+ * Copyright (c) 2015, 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.instrument;
+
+import com.oracle.truffle.api.instrument.ProbeNode.WrapperNode;
+import com.oracle.truffle.api.nodes.*;
+import com.oracle.truffle.api.nodes.NodeUtil.NodeField;
+
+/**
+ * Description of a failed attempt to instrument an AST node.
+ */
+public final class ProbeFailure {
+
+    public enum Reason {
+
+        /**
+         * Node to be probed has no parent.
+         */
+        NO_PARENT("Node to be probed has no parent"),
+
+        /**
+         * The node to be probed is a wrapper.
+         */
+        WRAPPER_NODE("The node to be probed is a wrapper"),
+
+        /**
+         * The node to be probed returned {@link Node#isInstrumentable()}{@code == false}.
+         */
+        NOT_INSTRUMENTABLE("The node to be project is \"not instrumentable\""),
+
+        /**
+         * No wrapper could be created that is also a {@link Node}.
+         */
+        NO_WRAPPER("No wrapper could be created"),
+
+        /**
+         * Wrapper not assignable to the parent's child field.
+         */
+        WRAPPER_TYPE("Wrapper not assignable to parent's child field"),
+
+        /**
+         * Attempt to \"probe lite\" an already probed node.
+         */
+        LITE_VIOLATION("Attempt to \"probe lite\" an already probed node");
+
+        final String message;
+
+        private Reason(String message) {
+            this.message = message;
+        }
+
+        public String getMessage() {
+            return message;
+        }
+    }
+
+    private final Reason reason;
+    private final Node parent;
+    private final Node child;
+    private final Object wrapper;
+
+    /**
+     * Description of an internal failure of {@link Node#probe()}.
+     *
+     * @param reason what caused the failure
+     * @param parent the parent, if known, of the child being probed
+     * @param child this child being probed
+     * @param wrapper the {@link WrapperNode} created to implement the probe
+     */
+    public ProbeFailure(Reason reason, Node parent, Node child, Object wrapper) {
+        this.reason = reason;
+        this.parent = parent;
+        this.child = child;
+        this.wrapper = wrapper;
+    }
+
+    /**
+     * @return a short explanation of the failure
+     */
+    public Reason getReason() {
+        return reason;
+    }
+
+    /**
+     * @return the parent, if any, of the node being probed
+     */
+    public Node getParent() {
+        return parent;
+    }
+
+    /**
+     * @return the node being probed
+     */
+    public Node getChild() {
+        return child;
+    }
+
+    /**
+     * @return the {@link WrapperNode} created for the probe attempt
+     */
+    public Object getWrapper() {
+        return wrapper;
+    }
+
+    public String getMessage() {
+        final StringBuilder sb = new StringBuilder(reason.message + ": ");
+        if (parent != null) {
+            sb.append("parent=" + parent.getClass().getSimpleName() + " ");
+            if (child != null) {
+                sb.append("child=" + child.getClass().getSimpleName() + " ");
+                final NodeField field = NodeUtil.findChildField(parent, child);
+                if (field != null) {
+                    sb.append("field=" + field.getName() + " ");
+                }
+            }
+        }
+        if (wrapper != null) {
+            sb.append("wrapper=" + wrapper.getClass().getSimpleName());
+        }
+        return sb.toString();
+    }
+
+}