recursive-types.ts

type Pin<X extends Record<string, Record<string, keyof X>>> = {
	[Obj in keyof X]: {
		[F in keyof X[Obj]]: Pin<X>[X[Obj][F]]
	}
};

type Loopy = Pin<{
	one: {
		a: "one",
		b: "two",
	},

	two: {
		c: "one",
		d: "two",
	},
}>;

function descend(loopy: Loopy) {
	return loopy.one.a.a.b.c.a.b.c.b.d;
}