If you need a safe tagged union, you should be using enum: https://doc.rust-lang.org/reference/items/enumerations.html https://doc.rust-lang.org/reference/items

If you need a safe tagged union, you should be using enum: https://doc.rust-lang.org/reference/items/enumerations.html https://doc.rust-lang.org/reference/items/enumerations.html Unsafe unions are for the C-style type-punning unions, which are intrinsically unsafe.