AI solution for TypeScript puzzle on BFE.dev
39. implement ToNumber<T>

Solution:

type ToNumber<T extends string> = 
    T extends '0' ? 0 :
    T extends '1' ? 1 :
    T extends '2' ? 2 :
    T extends '3' ? 3 :
    T extends '4' ? 4 :
    T extends '5' ? 5 :
    T extends '6' ? 6 :
    T extends '7' ? 7 :
    T extends '8' ? 8 :
    T extends '9' ? 9 :
    never;

type A = ToNumber<'1'> // 1
type B = ToNumber<'40'> // 40
type C = ToNumber<'0'> // 0

In the above solution, we use conditional types to check whether the given string is a digit or not. We also use never to provide type safety to our solution.