setTrace method
During a parse is sometimes useful to listen in on the rule entry and exit events as well as token matches. This is for quick and dirty debugging.
Implementation
void setTrace(bool trace) {
if (!trace) {
removeParseListener(_tracer);
_tracer = null;
} else {
if (_tracer != null) {
removeParseListener(_tracer);
} else {
_tracer = TraceListener(this);
}
addParseListener(_tracer!);
}
}