# 4522 Issues with Emitted JavaScript Code with Certain Complex Unit Dependencies

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I have a class hierarchy that is a tad complex. At the root I have TEditableDataItem which has:

class function GetDataTypeString : String; virtual;

I then have a variety of classes that derive from it, including TLibraryCommon which has more descendants which redefine it. At the bottom if uLibraryCommon, which has some of the descendant definitions in, there is:

class function TLibraryCommon.GetDataTypeString : String; begin Result := 'LIBCOMMONERROR'; Assert(false, 'Lib common error'); end;

class function TLibraryLabour.GetDataTypeString : String; begin Result := 'lib.lLab'; end;

In uLibraryMaterial, which defines a derived TLibraryMaterial, I have:

class function TLibraryMaterial.GetDataTypeString : String; begin Result := 'lib.lMat'; end;

The JSON output though has:

ulibrarycommon_tlibrarylabour.$p.getdatatypestring = function()
{
var $t = this;
return "lib.lLab";
};

ulibrarymaterial_tlibrarymaterial.$p.getdatatypestring1 = function()
{
var $t = this;
return "lib.lMat";
};

The key being, the compiler seems to have been confused and thinks that the material has its own custom version of the function, so the TLibraryCommon version is used instead, which causes a failure in my code.