IModelElement implementation to return from selection engine if correct model element couldn't be identified (similar to LocalVariable)
diff --git a/core/plugins/org.eclipse.dltk.core/model/org/eclipse/dltk/core/model/UnresolvedElement.java b/core/plugins/org.eclipse.dltk.core/model/org/eclipse/dltk/core/model/UnresolvedElement.java
new file mode 100644
index 0000000..6c33b58
--- /dev/null
+++ b/core/plugins/org.eclipse.dltk.core/model/org/eclipse/dltk/core/model/UnresolvedElement.java
@@ -0,0 +1,186 @@
+/*******************************************************************************
+ * Copyright (c) 2011 NumberFour AG
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     NumberFour AG - initial API and Implementation (Alex Panchenko)
+ *******************************************************************************/
+package org.eclipse.dltk.core.model;
+
+import java.util.HashMap;
+
+import org.eclipse.core.resources.IResource;
+import org.eclipse.core.runtime.IPath;
+import org.eclipse.core.runtime.IProgressMonitor;
+import org.eclipse.dltk.core.IBuffer;
+import org.eclipse.dltk.core.IModelElement;
+import org.eclipse.dltk.core.IOpenable;
+import org.eclipse.dltk.core.ISourceRange;
+import org.eclipse.dltk.core.ISourceReference;
+import org.eclipse.dltk.core.ModelException;
+import org.eclipse.dltk.core.SourceRange;
+import org.eclipse.dltk.core.WorkingCopyOwner;
+import org.eclipse.dltk.internal.core.ModelElement;
+import org.eclipse.dltk.internal.core.SourceRefElement;
+import org.eclipse.dltk.internal.core.util.MementoTokenizer;
+import org.eclipse.dltk.internal.core.util.Util;
+
+public class UnresolvedElement extends SourceRefElement {
+
+	private final String name;
+	private final int start, end;
+
+	/**
+	 * @param parent
+	 *            the parent of the element
+	 * @param name
+	 *            the name of the element
+	 * @param start
+	 *            the position of the element name start
+	 * @param end
+	 *            the position of the element name end (including - the position
+	 *            of the last character)
+	 */
+	public UnresolvedElement(IModelElement parent, String name, int start,
+			int end) {
+		super((ModelElement) parent);
+		this.name = name;
+		this.start = start;
+		this.end = end;
+	}
+
+	@Override
+	protected void closing(Object info) {
+		// an unresolved element has no info
+	}
+
+	@Override
+	protected Object createElementInfo() {
+		// an unresolved element has no info
+		return null;
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (!(o instanceof UnresolvedElement))
+			return false;
+		final UnresolvedElement other = (UnresolvedElement) o;
+		return this.start == other.start && this.end == other.end
+				&& super.equals(o);
+	}
+
+	@Override
+	public boolean exists() {
+		return this.parent.exists();
+	}
+
+	@Override
+	protected void generateInfos(Object info, HashMap newElements,
+			IProgressMonitor pm) {
+		// an unresolved element has no info
+	}
+
+	@Override
+	public IModelElement getHandleFromMemento(String token,
+			MementoTokenizer memento, WorkingCopyOwner owner) {
+		switch (token.charAt(0)) {
+		case JEM_COUNT:
+			return getHandleUpdatingCountFromMemento(memento, owner);
+		}
+		return this;
+	}
+
+	@Override
+	public void getHandleMemento(StringBuffer buff) {
+		((ModelElement) getParent()).getHandleMemento(buff);
+		buff.append(getHandleMementoDelimiter());
+		buff.append(this.name);
+		buff.append(JEM_COUNT);
+		buff.append(this.start);
+		buff.append(JEM_COUNT);
+		buff.append(this.end);
+		if (this.occurrenceCount > 1) {
+			buff.append(JEM_COUNT);
+			buff.append(this.occurrenceCount);
+		}
+	}
+
+	@Override
+	protected char getHandleMementoDelimiter() {
+		return ModelElement.JEM_LOCALVARIABLE;
+	}
+
+	@Override
+	public IResource getCorrespondingResource() {
+		return null;
+	}
+
+	@Override
+	public String getElementName() {
+		return this.name;
+	}
+
+	public int getElementType() {
+		return LOCAL_VARIABLE;
+	}
+
+	@Override
+	public IPath getPath() {
+		return this.parent.getPath();
+	}
+
+	/**
+	 * @see ISourceReference
+	 */
+	@Override
+	public String getSource() throws ModelException {
+		IOpenable openable = this.parent.getOpenableParent();
+		IBuffer buffer = openable.getBuffer();
+		if (buffer == null) {
+			return null;
+		}
+		ISourceRange range = getSourceRange();
+		int offset = range.getOffset();
+		int length = range.getLength();
+		if (offset == -1 || length == 0) {
+			return null;
+		}
+		try {
+			return buffer.getText(offset, length);
+		} catch (RuntimeException e) {
+			return null;
+		}
+	}
+
+	@Override
+	public ISourceRange getSourceRange() {
+		return new SourceRange(this.start, this.end - this.start + 1);
+	}
+
+	@Override
+	public IResource getUnderlyingResource() throws ModelException {
+		return this.parent.getUnderlyingResource();
+	}
+
+	@Override
+	public int hashCode() {
+		return Util.combineHashCodes(this.parent.hashCode(), this.start);
+	}
+
+	@Override
+	public boolean isStructureKnown() throws ModelException {
+		return true;
+	}
+
+	@Override
+	protected void toStringInfo(int tab, StringBuffer buffer, Object info,
+			boolean showResolvedInfo) {
+		buffer.append(tabString(tab));
+		toStringName(buffer);
+	}
+
+}