#![feature(untagged_unions)] #![allow(dead_code)] #![deny(unions_with_drop_fields)] union U { a: u8, // OK } union W { a: String, //~ ERROR union contains a field with possibly non-trivial drop code 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 union contains a field with possibly non-trivial drop code } // We don't know if `T` is trivially-destructable or not until trans union J { a: T, //~ ERROR union contains a field with possibly non-trivial drop code } union H { a: T, // OK, `T` is `Copy`, no destructor } fn main() {}