签名特质的联合，详细说明

这些类型通常在你需要运行时接受几种签名和验证方案时发挥作用（例如：BLS或EdDSA，见下文）。在这种情况下，可以声明一个由三个枚举类型组成的元组，每个枚举类型描述这些替代方案的“求和类型”（coproduct）。这实际上是一种签名方案（它具有规范签名、签名和验证密钥类型，并通过平凡的分配验证所有预期的属性）。

以下宏在以下两个条件下让你可以简单地定义这种类型的联合

• 枚举的变体标记具有相同的名称，即如果SignatureUnion的BLS变体是SignatureUnion::BLS(BLS12381Signature)，那么BLS的PublicKeyUnion变体也必须是PublicKeyUnion::BLS,
• 您为每个三个联合指定关联类型PrivateKeyType、SignatureType和PublicKeyType。 PrivateKeyType为VerifyingKeyMaterial和PublicKeyMaterial关联类型提供值，PublicKeyType为SigningKeyMaterial和PrivateKeyMaterial关联类型提供值，而SignatureType为SignatureMaterial关联类型提供值。

示例

# #[macro_use] extern crate crypto-derive;
use diem_crypto::{
    hash::HashValue,
    bls12381::{BLS12381PrivateKey, BLS12381PublicKey, BLS12381Signature},
    ed25519::{Ed25519PrivateKey, Ed25519PublicKey, Ed25519Signature},
};
use diem_crypto_derive::{
    SilentDebug, PrivateKey, PublicKey, Signature, SigningKey, ValidCryptoMaterial, VerifyingKey,
};

/// Generic public key enum
#[derive(
    Debug, Clone, PartialEq, Eq, Hash, ValidCryptoMaterial, PublicKey, VerifyingKey,
)]
#[PrivateKeyType = "GenericPrivateKey"]
#[SignatureType = "GenericSignature"]
pub enum GenericPublicKey {
    /// Ed25519 public key
    Ed(Ed25519PublicKey),
    /// BLS12-381 public key
    BLS(BLS12381PublicKey),
}
/// Generic private key enum
#[derive(SilentDebug, ValidCryptoMaterial, PrivateKey, SigningKey)]
#[PublicKeyType = "GenericPublicKey"]
#[SignatureType = "GenericSignature"]
pub enum GenericPrivateKey {
    /// Ed25519 private key
    Ed(Ed25519PrivateKey),
    /// BLS12-381 private key
    BLS(BLS12381PrivateKey),
}
/// Generic signature enum
#[allow(clippy::large_enum_variant)]
#[derive(Clone, Debug, PartialEq, Eq, Hash, Signature)]
#[PrivateKeyType = "GenericPrivateKey"]
#[PublicKeyType = "GenericPublicKey"]
pub enum GenericSignature {
    /// Ed25519 signature
    Ed(Ed25519Signature),
    /// BLS12-381 signature
    BLS(BLS12381Signature),
}