On the old fsf machine* I used Emacs as my login shell (in /etc/passwd), but this takes it to a whole new level. Outstanding!
* yes there was a time when the fsf’s only computer was a fax 750 (“soon to be running gnu”)
* yes there was a time when the fsf’s only computer was a fax 750 (“soon to be running gnu”)
But on ITS, the PDP-10 OS we mostly used until the mid 80s, DDT (the debugger) was the shell. There were no core dumps for interactive programs; if your program halted abnormally you were already in the debugger so it was no big deal. The Lispm, of course, worked this way too although the debugger was more sophisticated than DDT.