Nightly Ungil implementation prevents use of objects with lifetimes

[michprev]

Hey!
I need to have a member with lifetime inside pyclass. As a workaround, I am using static lifetime:

#[pyclass(unsendable)]
pub struct Chain {
    pub evm: Option<Arc<Mutex<Evm<'static, (), DB>>>>,
}

At the same time, the Evm struct does not implement Send and may use tokio with multiple processes so I need to call py.allow_threads before working with it. Since Evm does not implement Send, I switched to nightly rust where Ungil is implemented through auto traits.

However, the new Ungil implementation still does not allow me to pass Evm into the closure.

A minimal example without actually involving Chain struct:

#[pyfunction]
fn get_balance(py: Python) -> BigUint {
    let tmp = Arc::new(Mutex::new(Evm::builder().with_db(DB::EmptyDB(revm::db::CacheDB::new(EmptyDB::new()))).build()));
    let mut evm = tmp.lock().unwrap();

    py.allow_threads(move || {
        evm.transact()
    });

    BigUint::ZERO
}

This raises a lot of errors, one of them - https://pastebin.com/KN3PbZR2.

Any idea what is happening or what would be a good workaround?

[michprev]

Turned out it's probably because negative auto traits are not implemented for dyn traits by default - https://stackoverflow.com/questions/76465714/making-a-negative-trait-in-rust-opposite-of-sized-unsized