use std::mem::ManuallyDrop; union U1 { // OK a: u8, } union U2<T: Copy> { // OK a: T, } union U22<T> { // OK a: ManuallyDrop<T>, } union U23<T> { // OK a: (ManuallyDrop<T>, i32), } union U24<T> { // OK a: [ManuallyDrop<T>; 2], } union U3 { a: String, //~ ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union } union U32 { // field that does not drop but is not `Copy`, either a: std::cell::RefCell<i32>, //~ ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union } union U4<T> { a: T, //~ ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union } union U5 { // Having a drop impl is OK a: u8, } impl Drop for U5 { fn drop(&mut self) {} } union U5Nested { // a nested union that drops is NOT OK nest: U5, //~ ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union } union U5Nested2 { // for now we don't special-case empty arrays nest: [U5; 0], //~ ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union } union U6 { // OK s: &'static i32, m: &'static mut i32, } union U7<T> { // OK f: (&'static mut i32, ManuallyDrop<T>, i32), } union U8<T> { // OK f1: [(&'static mut i32, i32); 8], f2: [ManuallyDrop<T>; 2], } fn main() {}