Macro ffi_enum 

macro_rules! ffi_enum {
    (
        $(#[$meta:meta])*
        $vis:vis enum $name:ident : $raw:ty {
            $( $(#[$vmeta:meta])* $variant:ident = $value:path ),+ $(,)?
        }
    ) => { ... };
}

Declares a Rust enum mirroring a C enum, together with From/TryFrom conversions to and from the raw type.

ffi_enum! {
    /// Docs.
    pub enum NeighborMode: igraph_neimode_t {
        /// Out-neighbors.
        Out = igraph_neimode_t_IGRAPH_OUT,
    }
}