The Primitive Type never
In this lesson, you will see the type never, which is used to indicate that something must never happen.
We'll cover the following...
The type never means that nothing occurs. It is used when a type guard cannot occur or in a situation where an exception is always thrown. There is a difference between void and never. A function that has the explicit return type of never won’t allow your code to return undefined, which is different from a void function that allows code to return undefined.
function functionThrow(): never {throw new Error("This function return never");}
The never type is a subtype for every type. Hence, you can return never (for example, throwing an exception) when a return type is specified to be void or string, but cannot return a string when explicitly marked as never.
TypeScript can benefit from the never type by performing an exhaustive check. An exhaustive ...