docs: private boolean markAsDeadCode(XExpression expression) {
  		if (expression instanceof XBlockExpression) {
  			final XBlockExpression block = (XBlockExpression) expression;
  			final EList<XExpression> expressions = block.getExpressions();
  			if (!expressions.isEmpty()) {
  				markAsDeadCode(expressions.get(0));
  				return true;
  			}
  		}
  		if (expression != null) {
  			error("Unreachable expression.", expression, null, IssueCodes.UNREACHABLE_CODE); //$NON-NLS-1$
  			return true;
  		}
  		return false;
  	}