Rust try 向下转换时出现终身错误

我有一个错误的链接列表，我正在try 遍历这些错误.

type BoxedError = Box<dyn std::error::Error + Send + Sync + 'static>;

#[derive(Debug)]
struct MyError {
    code: Option<u32>,
    source: Option<BoxedError>,
}

impl std::error::Error for MyError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        self.source().map(|s| s as _)
    }
}

impl std::fmt::Display for MyError {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        std::fmt::Display::fmt("", f)
    }
}

impl MyError {
    fn source(&self) -> Option<&(dyn std::error::Error + Send + Sync + 'static)> {
        self.source.as_ref().map(|c| c.as_ref())
    }

    fn traverse(&self) -> Option<u32> {
        use core::any::Any;
        if let Some(code) = self.code {
            return Some(code);
        }    
        if let Some(source) = self.source() {
            let as_any = &source as &dyn Any;
            if let Some(myerr) = as_any.downcast_ref::<MyError>() {
                return myerr.traverse();
            }
        }
        None
    }
}

这会产生以下错误:

error[E0759]: `self` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
  --> src/lib.rs:31:36
   |
26 |     fn traverse(&self) -> Option<u32> {
   |                 ----- this data with an anonymous lifetime `'_`...
...
31 |         if let Some(source) = self.source() {
   |                               ---- ^^^^^^
   |                               |
   |                               ...is used here...
32 |             let as_any = &source as &dyn Any;
   |                          ------- ...and is required to live as long as `'static` here

For more information about this error, try `rustc --explain E0759`.
error: could not compile `playground` due to previous error

考虑到源函数返回一个静态trait对象(这意味着该对象后面没有其他引用，对吗？)，我不知道为什么会出现终身错误.