I want separate bibliograhies for phdtheses and masterstheses in biblatex 3.0.
The bib-keys @phdthesis and @masterthesis will be treated just like @thesis by biblatex (with an additional bib-field "type").
Thus
\printbibliography[type=thesis, heading=subbibliography, title={Theses}]
collects all kind of theses. And
\printbibliography[type=phdthesis, heading=subbibliography, prefixnumbers=P, title={Doctoral Theses}]
\printbibliography[type=mastersthesis, heading=subbibliography, prefixnumbers=M, title={Master's Theses}]
throws a warning
Package biblatex Warning: Type 'phdthesis' not found ...
What can I do to separate phdtheses and masterstheses automatically? Is it possible to filter by the bib-field "type" (not the bib-key)?

