constructor(textModel, bracketTokens) {
        this.textModel = textModel;
        this.bracketTokens = bracketTokens;
        this.reader = new NonPeekableTextBufferTokenizer(this.textModel, this.bracketTokens);
        this._offset = lengthZero;
        this.didPeek = false;
        this.peeked = null;
        this.textBufferLineCount = textModel.getLineCount();
        this.textBufferLastLineLength = textModel.getLineLength(this.textBufferLineCount);
    }
If this token is an opening bracket, this just contains `bracketId`.
If this token is a closing bracket, this lists all opening bracket ids, that it closes.
Otherwise, it is empty.