pub fn ptr_eq(&self, rhs: &Self) -> bool {
        let lhs = match self.inner.as_ref() {
            Some(lhs) => lhs,
            None => return false,
        };
        let rhs = match rhs.inner.as_ref() {
            Some(rhs) => rhs,
            None => return false,
        };
        Arc::ptr_eq(lhs, rhs)
    }
Returns `true` if the two `Shared`s point to the same future (in a vein similar to
`Arc::ptr_eq`).

Returns `false` if either `Shared` has terminated.
futures-util/src/future/future/shared.rs