TagChunk constructor
Construct a new instance of TagChunk using the specified label and tag.
@param label The label for the tag. If this is null, the TagChunk represents an unlabeled tag. @param tag The tag, which should be the name of a parser rule or token type.
@exception ArgumentError if tag is null or empty.
Implementation
TagChunk(this.tag, {this.label}) {
if (tag.isEmpty) {
throw ArgumentError.value(tag, 'tag', 'cannot be empty');
}
}