src/vs/editor/contrib/linesOperations/linesOperations.ts/BackwardsCompatibleRegExp/get
class BackwardsCompatibleRegExp:	public get(): RegExp | null {
		if (!this._evaluated) {
			this._evaluated = true;
			try {
				this._actual = new RegExp(this._pattern, this._flags);
			} catch (err) {
				// this browser does not support this regular expression
			}
		}
		return this._actual;
	}