// If we got more than one child, report that the databinding expression
        // is invalid. It must be a single expression.
        else if (n > 1)
        {
            final ICompilerProblem problem = new MXMLInvalidDatabindingExpressionProblem(fileNode);
            problems.add(problem);
            return null;
        }
        IASNode firstChild = fileNode.getChild(0);
        // If we got a single child but it isn't an expression,
        // report a problem.
        if (!(firstChild instanceof IExpressionNode))
        {
            final ICompilerProblem problem = new MXMLInvalidDatabindingExpressionProblem(fileNode);
            problems.add(problem);
            return null;
        }
        // We got a single expression, so return it.