Section 3 - Filling
filling it with is an action applying to two visible things.
Understand "fill [thing] with [thing]" as filling it with.
filling is an action applying to one visible thing.
Understand "fill [thing]" as filling.
Carry out filling:
try filling the noun with the river.
Check filling a thing with something:
if the noun is not a vessel:
say "You can't fill that.";
stop the action;
otherwise:
if the second noun is not the river:
say "You can't fill [the noun] with that.";
stop the action.
Check filling a vessel with something when the noun is full:
say "[The noun] is already full.";
stop the action;
Carry out filling a vessel with the river:
now the noun is full;
say "[The noun] is now full.".