finish is the position just after the last character of the
input for the positioned value.
Set the finish position if it is NoPosition, otherwise leave
it unchanged.
Set the finish position if it is NoPosition, otherwise leave
it unchanged. Return the new positioned value.
Set both the start and finish positions from the given
Positioned value, if they are, individually, NoPosition,
otherwise leave them unchanged.
Set the start position if it is NoPosition, otherwise leave
it unchanged.
Set the start position if it is NoPosition, otherwise leave
it unchanged. Return the new positioned value.
start is the position just before the input for the positioned
value starts, ignoring any whitespace if the relevant parser is
skipping it.
Class to keep track of line and column positions. We keep track of both the
startandfinishposition.