Support generics, enums with non-unit variants, and opaque structs.

[sean1708]

Support generics, enums with non-unit variants, and opaque structs.

[Sean1708]

See here for info on representation.

[Sean1708]

The docs suggest using an empty enum for opaque structs, but these can't be #[repr(C)].

What about unit structs?

[Sean1708]

Even the enum would be easy enough to support, just check the variants are empty before checking for #[repr(C)] and special case that.

[Sean1708]

Thinking about it, you can't use empty enums for opaque structs because they need to be not opaque on the Rust side.

Instead I think private #[repr(C)] structs should be opaque structs.

[Sean1708]

The two current thoughts for opaque structs are

struct NonOpaque {
    b: f64,
}

// typedef struct Opaque Opaque;
#[repr(C)]
pub struct Opaque(NonOpaque);

À la this playground. So any public #[repr(C)] newtype would be an opaque struct that would have to be handled via pointers in C.

Alternatively have any public #[repr(C)] struct with only private members be an opaque struct, this feels too magic to me though.

[Sean1708]

Closed by b6a7cc1