57     source: Option<Box<dyn core::error::Error + Send + Sync + 'static>>,  field
67     fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {  in source()  method
68         let source = self.source.as_ref()?;  in source()  localVariable
69         Some(&**source)  in source()
76         source: Option<Box<dyn core::error::Error + Send + Sync + 'static>>,  in new()
79         Self { message, source }  in new()
162     let error = error.source().unwrap();  in into_boxed_dyn_error()
165     let error = error.source().unwrap();  in into_boxed_dyn_error()
168     assert!(error.source().is_none());  in into_boxed_dyn_error()
851     assert!(root.source().is_none());  in root_cause()
866         fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {  in chain_with_leaf_sources()  method