fn never_error(self) -> NeverError<Self>
    where
        Self: Sized,
    {
        assert_future::<Result<Self::Output, Infallible>, _>(NeverError::new(self))
    }
Turns a [`Future<Output = T>`](Future) into a
[`TryFuture<Ok = T, Error = Never`>](futures_core::future::TryFuture).
futures-util/src/future/future/mod.rs