Indicates that a terminal action has been performed. Rule processing must stop.
Valid from either Matcher or Action, however it must originate only from
an Action and may be propagated up the stack through Matcher.
We are favoring this propagation of return over exceptions.
Returns the enum constant of this type with the specified name.
The string must match exactly an identifier used to declare an
enum constant in this type. (Extraneous whitespace characters are
name - the name of the enum constant to be returned.