I'd be very much in favor and I'd be happy to contribute changes for this. I've added type hints in my local fork to assist in development. Especially for core utility functions like idx and id which otherwise completely hide type information.

Tools make no mistakes.

Remove first person voice in a few areas. And a bit of swearing that slipped through from my notes.

@valerio.bozzolan looks to not change behavior in mercurial at all :) I'm not in Trusted Contributors so I can't accept.

A comment in two parts:
First and most relevant to this task: It certainly would be nice to get some of this into documentation! It took me quite awhile to figure this out when doing my own extension development.