Bug 52346 [misc] Undo yields wrong code
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitEditor.java
import org.eclipse.jface.dialogs.ErrorDialog;
import org.eclipse.jface.dialogs.IMessageProvider;
import org.eclipse.jface.dialogs.MessageDialog;
import org.eclipse.jface.preference.IPreferenceStore;
import org.eclipse.jface.util.ListenerList;
import org.eclipse.jface.util.PropertyChangeEvent;
import org.eclipse.jface.window.Window;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.BadPositionCategoryException;
import org.eclipse.jface.text.DocumentCommand;
import org.eclipse.jface.text.IAutoEditStrategy;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IDocumentExtension;
import org.eclipse.jface.text.IDocumentListener;
import org.eclipse.jface.text.ILineTracker;
import org.eclipse.jface.text.IPositionUpdater;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.ITextOperationTarget;
import org.eclipse.jface.text.ITextViewerExtension;
import org.eclipse.jface.text.ITypedRegion;
import org.eclipse.jface.text.IWidgetTokenKeeper;
import org.eclipse.jface.text.Position;
import org.eclipse.jface.text.TextUtilities;
import org.eclipse.jface.text.contentassist.ContentAssistant;
import org.eclipse.jface.text.contentassist.IContentAssistant;
import org.eclipse.jface.text.contentassist.IContentAssistantExtension;
import org.eclipse.jface.text.link.ExclusivePositionUpdater;
import org.eclipse.jface.text.link.ILinkedListener;
import org.eclipse.jface.text.link.LinkedEnvironment;
import org.eclipse.jface.text.link.LinkedPositionGroup;