Rust AES thing: https://www.reddit.com/r/rust/comments/tvfmxv/how_to_use_sized_traits_in_structs/

aes_thingy.rs

use aes::cipher::{
    generic_array::GenericArray, BlockCipher, BlockDecrypt, BlockEncrypt, KeyInit, KeySizeUser,
};
use aes::{Aes128, Aes192};

#[derive(Debug, Clone)]
struct Testy<CI> {
    cipher: CI,
    data: Vec<u8>,
}

trait CipherTraitBundle: BlockCipher + BlockEncrypt + BlockDecrypt + KeyInit + KeySizeUser {}

impl CipherTraitBundle for Aes128 {}
impl CipherTraitBundle for Aes192 {}

impl<CI: CipherTraitBundle> Testy<CI> {
    pub fn new(key: GenericArray<u8, <CI as KeySizeUser>::KeySize>) -> Self {
        Self {
            cipher: <CI as KeyInit>::new(&key),
            data: vec![],
        }
    }

    pub fn encode(&mut self) {
        self.cipher
            .encrypt_block(GenericArray::from_mut_slice(self.data.as_mut_slice()));
    }

    pub fn decode(&self) -> Vec<u8> {
        let mut output = self.data.clone();
        self.cipher
            .decrypt_block(GenericArray::from_mut_slice(output.as_mut_slice()));
        output
    }
}

fn encode_any_testy<CI: CipherTraitBundle>(arg: &mut Testy<CI>) {
    arg.encode();
}

fn main() {
    let mut x = Testy::<Aes128>::new(GenericArray::from([0u8; 16]));
    x.data = (0..16).collect();
    println!("x: Before encode: {:?}", x);
    encode_any_testy(&mut x);
    let x_decoded = x.decode();
    println!("x: After encode: {:?} => {:?}", x, x_decoded);

    let mut y = Testy::<Aes192>::new(GenericArray::from([0u8; 24]));
    println!("y: Before encode: {:?}", y);
    y.data = (0..16).collect();
    encode_any_testy(&mut y);
    let y_decoded = y.decode();
    println!("y: After encode: {:?} => {:?}", y, y_decoded);
}

output.txt

x: Before encode: Testy { cipher: Aes128 { .. }, data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15] }
x: After encode: Testy { cipher: Aes128 { .. }, data: [122, 202, 15, 217, 188, 214, 236, 124, 159, 151, 70, 102, 22, 230, 162, 130] } => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
y: Before encode: Testy { cipher: Aes192 { .. }, data: [] }
y: After encode: Testy { cipher: Aes192 { .. }, data: [184, 26, 102, 73, 80, 0, 143, 145, 50, 62, 213, 59, 211, 48, 147, 41] } => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]