What does `type Tail = T extends [any, …infer Rest] ? Rest : never` compute?

Question

TypeScript Professional — Hard

What does `type Tail = T extends [any, …infer Rest] ? Rest : never` compute?

Accepted Answer

The computation `type Tail = T extends [any, ...infer Rest] ? Rest : never` in TypeScript Professional calculates the tuple type with the first element removed. This is achieved by checking if the type `T` extends a tuple with any first element and inferring the rest of the elements. If not, it returns `never`.