public static IFunctionInfo GetUserFunctionInfo(this AstRoot ast, string functionName, int position) {
var scope = ast.GetNodeOfTypeFromPosition<IScope>(position);
var v = scope?.FindFunctionDefinitionByName(functionName, position);
var rf = v?.Value as RFunction;
var fd = rf?.Value as IFunctionDefinition;
return fd?.MakeFunctionInfo(functionName);
}
}