Bug 42587 Left over from content assist
M3 - set preference that content assist should overwrite - open content assist on some word so that the rest of the word is indicated to be overwritten - transfer focus to the content assist widget using TAB - Esc -> overwrite indication is still there
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/link/contentassist/CompletionProposalPopup2.java
* @param offset the offset
	 * @param event the merged document event
	 * @return the set of filtered proposals
	 * @since 2.0
	 */
	private ICompletionProposal[] computeFilteredProposals(int offset, DocumentEvent event) {
		
		if (offset == fInvocationOffset && event == null)
			return fComputedProposals;
			
		if (offset < fInvocationOffset) {
			return null;
		}
		
		ICompletionProposal[] proposals= fComputedProposals;
		if (offset > fFilterOffset)
			proposals= fFilteredProposals;
			
		if (proposals == null)
			return null;
			
		IDocument document= fViewer.getDocument();
		int length= proposals.length;
		List filtered= new ArrayList(length);
		for (int i= 0; i < length; i++) {
				
			if (proposals[i] instanceof ICompletionProposalExtension2) {
				ICompletionProposalExtension2 p= (ICompletionProposalExtension2) proposals[i];				
				if (p.validate(document, offset, event))
					filtered.add(p);