src/vs/editor/common/model/bracketPairsTextModelPart/bracketPairsTree/parser.ts/Parser/parseDocument
class Parser:	parseDocument(): AstNode {
		this._itemsConstructed = 0;
		this._itemsFromCache = 0;

		let result = this.parseList(SmallImmutableSet.getEmpty());
		if (!result) {
			result = ListAstNode.getEmpty();
		}

		return result;
	}