if (this.lookahead.type === token_1.Token.Identifier && !this.hasLineTerminator) {
                label = this.parseVariableIdentifier();
                var key = '$' + label.name;
                if (!Object.prototype.hasOwnProperty.call(this.context.labelSet, key)) {
                    this.throwError(messages_1.Messages.UnknownLabel, label.name);