Bug 6700 Code assist should not just beep
suggest to show a status message: Could not complete due to syntax errors. This is also better for accessability reasons.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitEditor.java
/**
		 * Highlights the brackets.
		 */
		class HighlightBrackets implements PaintListener {
			
			private JavaPairMatcher fMatcher= new JavaPairMatcher(new char[] { '{', '}', '(', ')', '[', ']' });
			private Position fBracketPosition= new Position(0, 0);
			private int fAnchor;
			
			private boolean fIsActive= false;
			private StyledText fTextWidget;
			private Color fColor;
			
			
			public HighlightBrackets() {
				fTextWidget= fSourceViewer.getTextWidget();
			}
			
			public void setHighlightColor(Color color) {
				fColor= color;
			}
						
			public void dispose() {
				if (fMatcher != null) {
					fMatcher.dispose();
					fMatcher= null;
				}