ADD { Lemma a : True. }
ADD here { Proof using. }
ADD { fail. }
ADD { trivial. } # first error
ADD { Qed. }
WAIT
EDIT_AT here
# Fixing the proof
ADD fix { trivial. }
ADD { Qed. }
WAIT
EDIT_AT fix
ADD { Qed. }
EDIT_AT fix
ADD { Qed. }
JOIN