Hello, I need a static variable with a dummy value of !Sync type, but the type is !Sync because it has a vector of !Sync elements, so if the vector is empty then the value of a type is Sync. Is there some way / crate to express it without me writing unsafe?

pub struct Foo(pub Vec<Cell<u8>>);

// No way to get `&mut Foo` thus we can't append elements thus no `Cell` thus `Sync`.
static FOO: Foo = Foo(Vec::new());

fn bar(foo: &Foo) {
    for element in foo.0.iter() {
        element.update(|x| x.wrapping_add(1));
    }
}

bar(&'static FOO); // It is fine to use that dummy across the threads

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