r[type.never]
r[type.never.syntax]
Syntax
NeverType :!
r[type.never.intro]
The never type ! is a type with no values, representing the result of
computations that never complete.
Note
Because ! has no values, reading it from memory (or otherwise producing a value of the type at runtime) is immediate undefined behaviour.
r[type.never.coercion]
Expressions of type ! can be coerced into any other type.
r[type.never.constraint]
The ! type can only appear in function return types presently,
indicating it is a diverging function that never returns.
fn foo() -> ! {
panic!("This call never returns.");
}unsafe extern "C" {
pub safe fn no_return_extern_func() -> !;
}