多线程应用程序无法编译并出现错误链

我介绍了error-chain到以前工作的应用程序中。错误本身很清楚，std::error::Error + 'static缺乏实施trait std::marker::Send:

error[E0277]: the trait bound `std::error::Error + 'static: std::marker::Send` is not satisfied
  --> src/main.rs:35:5
   |
35 | /     error_chain!{
36 | |
37 | |         foreign_links {
38 | |             Mqttc(::mqttc::Error);
...  |
53 | |         }
54 | |     }
   | |_____^ `std::error::Error + 'static` cannot be sent between threads safely
   |
   = help: the trait `std::marker::Send` is not implemented for `std::error::Error + 'static`
   = note: required because of the requirements on the impl of `std::marker::Send` for `std::ptr::Unique<std::error::Error + 'static>`
   = note: required because it appears within the type `std::boxed::Box<std::error::Error + 'static>`
   = note: required because it appears within the type `mqttc::netopt::Error`
   = note: required because it appears within the type `mqttc::Error`
   = note: required because it appears within the type `errors::ErrorKind`
   = note: required because it appears within the type `errors::Error`
   = note: required by `error_chain::ChainedError`
   = note: this error originates in a macro outside of the current crate

我不知道如何解决这个问题。请注意，我使用的更多最新的分叉mqttc/mqtt3 https://github.com/amikhalev/rust-mq而不是上游的板条箱。

mqttc::Error包含一个mqttc::netopt::Error，其中又包含一个Box<std::error::Error>（脱糖到std::boxed::Box<std::error::Error + 'static>. std::error::Error这是一个特征对象。因为Error特质没有Send作为一个超级特征，实现Error不需要实施Send。所以，Box<std::error::Error>不执行Send因为不是所有类型T: std::error::Error实施Send.

这可以通过更改来解决mqttc::netopt::Error要使用的类型Box<std::error::Error + Send>代替Box<std::error::Error>（这对图书馆来说是一个重大改变）。