1 error[E0658]: unions with non-`Copy` fields other than `ManuallyDrop<T>` are unstable
2 --> $DIR/feature-gate-untagged_unions.rs:20:5
4 LL | a: std::cell::RefCell<i32>,
5 | ^^^^^^^^^^^^^^^^^^^^^^^^^^
7 = note: see issue #55149 <https://github.com/rust-lang/rust/issues/55149> for more information
8 = help: add `#![feature(untagged_unions)]` to the crate attributes to enable
10 error[E0740]: unions may not contain fields that need dropping
11 --> $DIR/feature-gate-untagged_unions.rs:16:5
16 help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
18 LL | a: std::mem::ManuallyDrop<String>,
19 | +++++++++++++++++++++++ +
21 error[E0740]: unions may not contain fields that need dropping
22 --> $DIR/feature-gate-untagged_unions.rs:24:5
27 help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
29 LL | a: std::mem::ManuallyDrop<T>,
30 | +++++++++++++++++++++++ +
32 error: aborting due to 3 previous errors
34 Some errors have detailed explanations: E0658, E0740.
35 For more information about an error, try `rustc --explain E0658`.