error: unions cannot have zero fields
  --> $DIR/eval-error.rs:14:1
   |
LL | union Foo2 {}
   | ^^^^^^^^^^^^^

error[E0517]: attribute should be applied to a struct or union
  --> $DIR/eval-error.rs:24:12
   |
LL |   #[repr(u8, packed)]
   |              ^^^^^^
LL |
LL | / enum Foo3 {
LL | |     A
LL | | }
   | |_- not a struct or union

error[E0277]: the size for values of type `str` cannot be known at compilation time
  --> $DIR/eval-error.rs:2:8
   |
LL |     a: str,
   |        ^^^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `str`
   = note: no field of a union may have a dynamically sized type
   = help: change the field's type to have a statically known size
help: borrowed types always have a statically known size
   |
LL |     a: &str,
   |        +
help: the `Box` type always has a statically known size and allocates its contents in the heap
   |
LL |     a: Box<str>,
   |        ++++   +

error[E0740]: field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
  --> $DIR/eval-error.rs:2:5
   |
LL |     a: str,
   |     ^^^^^^
   |
   = note: union fields must not have drop side-effects, which is currently enforced via either `Copy` or `ManuallyDrop<...>`
help: wrap the field type in `ManuallyDrop<...>`
   |
LL |     a: std::mem::ManuallyDrop<str>,
   |        +++++++++++++++++++++++   +

error[E0080]: evaluation of constant value failed
  --> $DIR/eval-error.rs:9:30
   |
LL |         let _: Option<Foo> = None;
   |                              ^^^^ the type `Foo` has an unknown layout

error: aborting due to 5 previous errors

Some errors have detailed explanations: E0080, E0277, E0517, E0740.
For more information about an error, try `rustc --explain E0080`.