Metagen package is used to describe structures, interfaces, functions, RPC calls using DSL. This can be useful for codegen, bindings, etc.

Here is an example of some imaginary DSL:

#include enum.meta

func GetPlayer(
    id : uint32
) : DataPlayer

func Apply(
    fn : func(float, DataPlayer) : uint32
)

struct DataPlayer
    @POD @table:player @pkey:id
    id                : uint32
    version           : string @strmax:16
    gold              : uint8 @default:0 #bonus
    registered        : bool @default:true

    func Equals(
        o : DataPlayer
        v : uint32
    ) : bool,bool
end

struct ProtoBase
    id    : uint32
    title : string @strmax:16 @default:"Hello"
end

struct ProtoBuilding extends ProtoBase
    floors : int32
    arr : uint32[] @default:[1,2,3]
end

Look at tests for an actual API usage.