Why and how to use never?

The never type is used to represent values that are never expected to occur or that are not intended to be used, such as the result of a function that always throws an exception or an infinite loop that never returns.

The never type is a useful way to express the absence of a value or the impossibility of a scenario, and it can help to prevent errors and improve code quality by indicating that a value or a function is not intended to be used or accessed.

function fail(message: string): never {
    throw new Error(message);
}

function infiniteLoop(): never {
    while (true) {}
}

let x: never = fail('Something went wrong');  // ok
let y: never = infiniteLoop();  // ok

let z: number = x;  // error: Type 'never' is not assignable to type 'number'
let w: string = x;  // error: Type 'never' is not assignable to type 'string'