npm install ts-morph currently installs 1.3.5 which shows as published 17 hours ago. It's missing a lot of stuff. I lost part of my sanity this morning trying to figure out what was going on in my code.
Jeez. I would have thought it would keep whatever is the highest published version number as the latest.
Sorry about that and thanks for letting me know! Will fix this right away.
Fixed. Thanks so much once again for reporting!