What is the never type in Rust

The never type (written as !) is a special type in Rust that represents a function or expression that never returns a value because it either panics or loops infinitely. It is a subtype of every other type, allowing it to be used wherever any other type is expected to satisfy the compiler's type checking requirements.

fn crash() -> ! {
    panic!("This function never returns!");
}

fn loop_forever() -> ! {
    loop {
        // This loop never ends
    }
}

The never type is a way to tell Rust that a piece of code will never finish running normally. It usually happens when your program crashes or gets stuck in an endless loop. Think of it like a road that leads to a dead end; once you enter it, you can never come back out to the rest of the program.