Never type

^Syntax
NeverType : !

The never type ! is a type with no values, representing the result of computations that never complete. Expressions of type ! can be coerced into any other type.

let x: ! = panic!();
// Can be coerced into any type.
let y: u32 = x;

NB. The never type was expected to be stabilized in 1.41, but due to some last minute regressions detected the stabilization was temporarily reverted. The ! type can only appear in function return types presently. See the tracking issue for more details.