Rules that return more than a single value must return an object
containing all the values. Besides the properties defined in
RuleLabelScope.predefinedRulePropertiesScope there may be user-defined
return values. This class simply defines the minimum properties that
are always defined and methods to access the others that might be
available depending on output option such as template and tree.
Note text is not an actual property of the return value, it is computed
from start and stop using the input stream's toString() method. I
could add a ctor to this so that we can pass in and store the input
stream, but I'm not sure we want to do that. It would seem to be undefined
to get the .text property anyway if the rule matches tokens from multiple
I do not use getters for fields of objects that are used simply to
group values such as this aggregate. The getters/setters are there to
satisfy the superclass interface.