src/vs/base/common/functional.ts/once
export function once<T extends Function>(this: unknown, fn: T): T {
	const _this = this;
	let didCall = false;
	let result: unknown;

	return function () {
		if (didCall) {
			return result;
		}

		didCall = true;
		result = fn.apply(_this, arguments);

		return result;
	} as unknown as T;
}