It's actually not in the standard library, but you can write it yourself:

type Expect<T extends true> = T;

`T extends true` puts a type constraint on the parameter, which then needs to be assignable to the literal type `true` to type-check.

OK cool, now what about `Equal` :).

type Equal<A, B> = A extends B ? (B extends A ? true : false) : false;

Actually, this won't work with union types! The definition of `Equal` I use is this one:

type Equal<X, Y> = (<T>() => T extends X ? 1 : 2) extends < T >() => T extends Y ? 1 : 2 ? true : false;

Understanding this requires a bit more context, but I'll explain why we need something so complicated in the Advanced Union Types chapter :)

I picked it from https://github.com/type-challenges/type-challenges which is an awesome resource too

Nice.

Thanks! Hope you'll enjoy using it