Provided two lists of srcref objects, find the first srcrefs in r that
entirely encapsulate each respective srcref in l, returning a list of
indices of srcrefs in r for each srcref in l.
Provided two lists of srcref objects, find the first srcrefs in r that
entirely encapsulate each respective srcref in l, returning a list of
indices of srcrefs in r for each srcref in l.