And I'm sure of the size, because I have a test:
```rust

#[test]
fn anti_size_regression_verification() {
    // Verify that the `MaybeAction` has the same size as `Action`, that is,
    // that the enum variant optimization kicks in:
    assert_eq!(
        core::mem::size_of::<Action<()>>(),
        core::mem::size_of::<MaybeAction<()>>(),
    );

    // Verify the size of one action:
    assert_eq!(24, core::mem::size_of::<Action<()>>());
}
```