#![allow(dead_code)] union U { a: u8, // OK } union W { a: String, //~ ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union b: String, // OK, only one field is reported } struct S(String); // `S` doesn't implement `Drop` trait, but still has non-trivial destructor union Y { a: S, //~ ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union } // We don't know if `T` is trivially-destructable or not until trans union J { a: T, //~ ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union } union H { a: T, // OK, `T` is `Copy`, no destructor } fn main() {}