List.map return array and not typed List

[qballer]

I have the following code

function changeCollection(rawData:List<RawData>): List<Data> {
    let filtered:List<RawData> = rawData.filter((value)=>  true/** some condition */)
    console.log('Wo: ',  filtered) // looks good
    let mapped:List<Template> =  filtered.map(rawToData) // returns [] instead of List<Data>
    return mapped;
}
function rawToData(val:RawData):Data{/*Impel*/}