Transitioning to superset enum variant causes unnecessary copy

When I have an enum whose variants are superset of the previous ones, transitioning to the superset variant unnecessarily copies the entire variant instead of just changing discriminant and copying the new data over.

https://rust.godbolt.org/z/Mjeq3d4MW

Example

use std::mem::{ManuallyDrop, take};

type Param = ManuallyDrop<String>;

#[derive(Default)]
enum State {
    #[default]
    None,
    A([Param; 16]),
    B([Param; 16], Param),
    C([Param; 16], Param, Param),
}

impl State {
    #[unsafe(no_mangle)]
    fn transition(&mut self, param: Param) {
        let taken = take(self);
        *self = match taken {
            Self::None | Self::C { .. } => Self::None,
            Self::A(a) => Self::B(a, param),
            Self::B(a, b) => Self::C(a, b, param),
        };
    }
}

Start with the Rust Compiler Explorer example at https://rust.godbolt.org/z/Mjeq3d4MW and inspect the generated code for State::transition. Compare transitions between the enum variants and identify whether the superset transition still copies the existing array; done means the unnecessary copy is eliminated while the shown behavior remains correct.