Bug 43035 Smart Tab ends up at offset 0
Have a line that has an indent greater than it is required. Place cursor at the correct indent position. Press Tab. => Cursor ends up at the beginning of the document.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/actions/IndentAction.java
* @throws BadLocationException if the document got changed concurrently 
	 */
	private int indentLine(IDocument document, int line, JavaIndenter indenter, JavaHeuristicScanner scanner) throws BadLocationException {
		IRegion currentLine= document.getLineInformation(line);
		int offset= currentLine.getOffset();
		
		String indent= null;
		if (offset < document.getLength()) {
			ITypedRegion partition= TextUtilities.getPartition(document, IJavaPartitions.JAVA_PARTITIONING, offset);
			String type= partition.getType();
			if (partition.getOffset() < offset
					&& type.equals(IJavaPartitions.JAVA_DOC)
					|| type.equals(IJavaPartitions.JAVA_MULTI_LINE_COMMENT)) {
				
				
				
				
				IRegion previousLine= document.getLineInformation(line - 1);
				
				DocumentCommand command= new DocumentCommand() {
				};
				command.text= "\n"; 
				command.offset= previousLine.getOffset() + previousLine.getLength();
				new JavaDocAutoIndentStrategy(IJavaPartitions.JAVA_PARTITIONING).customizeDocumentCommand(document, command);
				int i= command.text.indexOf('*');
				if (i != -1)
					indent= command.text.substring(1, i);
				else
					indent= command.text.substring(1);
			}