Common fields for tagged union

[oovm]

Consider the following structure in rust notation:

enum Test {
    common: bool,
    A(u8),
    B(u8),
}

No effect on class like term.

But for tuple like term, it should be placed to which field?

Maybe it can be stipulated that it must be placed first or last

Put it in front of the tuple in an orderly manner, and insert it in the back

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Unsolved Question:

Assuming the above rules

let a = Test::A(true, 0);
let b = &a.common;  // Is it legal?
let c = &a.0;       // true
let d = &a.1;       // 0