// We need to opt into the `!` feature in order to trigger the // requirement that this is testing. #![feature(never_type)] #![allow(unused)] trait Deserialize: Sized { fn deserialize() -> Result; } impl Deserialize for () { fn deserialize() -> Result<(), String> { Ok(()) } } trait ImplementedForUnitButNotNever {} impl ImplementedForUnitButNotNever for () {} fn foo(_t: T) {} //~^ NOTE required by `foo` fn smeg() { let _x = return; foo(_x); //~^ ERROR the trait bound //~| NOTE the trait `ImplementedForUnitButNotNever` is not implemented //~| NOTE the trait is implemented for `()` } fn main() { smeg(); }