Editing the baseLanguage.mpr with MPS

Hi MPS team!

I'm trying to modify the baseLanguage itself and build my own custom MPS from sources.

I tried to simply open the MPS_SRC/baseLanguage/baseLanguage/baseLanguage.mpr project in MPS, but it works not the way I expected - the baseLanguage language is still marked as (packaged), I get some NPE's while trying to regenerate the language, plus wrong paths errors and so on. I guess I'm not doing it right.

I wonder how do you edit the baseLanguage itself?

Best wishes,

Alexander.