Derive Macro TransparentWrapper

#[derive(TransparentWrapper)]
{
    // Attributes available to this derive:
    #[bytemuck]
    #[transparent]
}

Derive the TransparentWrapper trait for a struct

The macro ensures that the struct follows all the the safety requirements for the TransparentWrapper trait.

The following constraints need to be satisfied for the macro to succeed

• The struct must be #[repr(transparent)]
• The struct must contain the Wrapped type
• Any ZST fields must be Zeroable.

If the struct only contains a single field, the Wrapped type will automatically be determined. If there is more then one field in the struct, you need to specify the Wrapped type using #[transparent(T)]. Due to technical limitations, the type in the #[transparent(Type)] needs to be the exact same token sequence as the corresponding type in the struct definition.

Examples

#[derive(Copy, Clone, TransparentWrapper)]
#[repr(transparent)]
#[transparent(u16)]
struct Test<T> {
  inner: u16,
  extra: PhantomData<T>,
}

If the struct contains more than one field, the Wrapped type must be explicitly specified.

#[derive(Copy, Clone, TransparentWrapper)]
#[repr(transparent)]
// missing `#[transparent(u16)]`
struct Test<T> {
  inner: u16,
  extra: PhantomData<T>,
}

Any ZST fields must be Zeroable.

struct NonTransparentSafeZST;

#[derive(TransparentWrapper)]
#[repr(transparent)]
#[transparent(u16)]
struct Test<T> {
  inner: u16,
  extra: PhantomData<T>,
  another_extra: NonTransparentSafeZST, // not `Zeroable`
}