RUST：为什么我可以使用此库中的上下文来使用::上下文？

Question

我正在尝试简化一些使用库。

更多详细信息，我正在使用他们的第一个来自他们的文档的加密示例从他们的文档中：

use psa_crypto::types::algorithm::{Aead, AeadWithDefaultLengthTag};
use psa_crypto::types::key::{Attributes, Type, Lifetime, Policy, UsageFlags};
use psa_crypto::operations::{key_management, aead};
let alg = Aead::AeadWithDefaultLengthTag(AeadWithDefaultLengthTag::Ccm);
let mut usage_flags: UsageFlags = Default::default();
usage_flags.set_encrypt();
let attributes = Attributes {
key_type: Type::Aes,
     bits: 0,
     lifetime: Lifetime::Volatile,
     policy: Policy {
         usage_flags,
         permitted_algorithms: alg.into(),
     },
};
psa_crypto::init().unwrap();
let my_key = key_management::import(attributes, None, &KEY_DATA).unwrap();
let output_buffer_size = attributes.aead_encrypt_output_size(alg.into(), INPUT_DATA.len()).unwrap();
let mut output_buffer = vec![0; output_buffer_size];
let length = aead::encrypt(my_key, alg, &NONCE, &ADDITIONAL_DATA, &INPUT_DATA, &mut output_buffer).unwrap();
output_buffer.resize(length, 0);

我使用Any Howhow :: Result将此代码放入函数中更多惯用代码。不幸的是，如果我尝试使用.context（“错误”）更改第一个UNWRAP，我会得到一个错误：

let my_key = key_management::import(attributes, None, &KEY_DATA).context("error")?;
                                                                 ^^^^^^^ method cannot be called on `Result<Id, psa_crypto::types::status::Error>` due to unsatisfied trait bounds


    |
504 | pub enum Result<T, E> {
    | --------------------- doesn't satisfy `_: anyhow::Context<Id, psa_crypto::types::status::Error>`
    |
   ::: /home/fedboz01/.cargo/registry/src/github.com-1ecc6299db9ec823/psa-crypto-0.9.1/src/types/status.rs:50:1
    |
50  | pub enum Error {
    | -------------- doesn't satisfy `_: anyhow::context::ext::StdError`
    |
    = note: the following trait bounds were not satisfied:
            `psa_crypto::types::status::Error: anyhow::context::ext::StdError`
            which is required by `Result<Id, psa_crypto::types::status::Error>: anyhow::Context<Id, psa_crypto::types::status::Error>`

此错误是什么意思？如何更改此代码以使其正常工作？

Answer 1

Any HOW ::错误要求它包装的错误实现std :: error ::错误:: error。 ::错误 没有实现该特征，因此，它又不会实现上下文扩展特征。

错误消息的这一部分暗示了这一点，尽管它有点模糊，因为它在std :: error :: error :: error :: error：

50  | pub enum Error {
    | -------------- doesn't satisfy `_: anyhow::context::ext::StdError`
    |
    = note: the following trait bounds were not satisfied:
            `psa_crypto::types::status::Error: anyhow::context::ext::StdError`
            which is required by `Result<Id, psa_crypto::types::status::Error>: anyhow::Context<Id, psa_crypto::types::status::Error>`

这似乎是psa_crypto std :: error :: error :: error :: error :: /代码>库。可能值得提交错误要求他们实施该特征。作为解决方法，您有几个选择：

• 因为psa_crypto ::类型:: status :: status :: error实施std :: fmt :: fmt :: debug您可以使用它来获得A 字符串错误消息：psa_crypto :: init（）。map_err（| e |格式！ >
• 更漂亮的解决方案是实现确实实现错误的包装类型（及其要求，display）。