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
public String showProposals(final boolean autoActivated) {
					
		if (fKeyListener == null) {
			fKeyListener= new KeyListener() {
				public void keyPressed(KeyEvent e) {
					if (!Helper2.okToUse(fProposalShell))
						return;
					
					if (e.character == 0 && e.keyCode == SWT.MOD1) {
						
						int index= fProposalTable.getSelectionIndex();
						if (index >= 0)
							selectProposal(index, true);
					}									
				}
				public void keyReleased(KeyEvent e) {
					if (!Helper2.okToUse(fProposalShell))
						return;
					if (e.character == 0 && e.keyCode == SWT.MOD1) {
						
						int index= fProposalTable.getSelectionIndex();
						if (index >= 0)
							selectProposal(index, false);
					}
				}
			};
		}
		final StyledText styledText= fViewer.getTextWidget();
		if (styledText != null && !styledText.isDisposed())
			styledText.addKeyListener(fKeyListener);