src/vs/editor/standalone/common/monarch/monarchLexer.ts/MonarchStackElement/_equals
class MonarchStackElement:	private static _equals(a: MonarchStackElement | null, b: MonarchStackElement | null): boolean {
		while (a !== null && b !== null) {
			if (a === b) {
				return true;
			}
			if (a.state !== b.state) {
				return false;
			}
			a = a.parent;
			b = b.parent;
		}
		if (a === null && b === null) {
			return true;
		}
		return false;
	}