The problem I met is the following. A trait algebra::ToBytes is not implemented for [u8; 65536] in the lib I use. When I try to implement it, I succeed to implement a trait bytes::ToBytes for type [u8; 65536] by using a macro. But I still got the message trait algebra::ToBytes is missing, in the end.
The trait with the name ToBytes is defined only once in the lib, it is done in the file I edit.
Open an issue / make a pull request. The cargo manual also has a section for temporarily using your fixed version, instead: Overriding Dependencies
You've submitted a fix to an upstream crate for a bug you found, but you'd like to immediately have your application start depending on the fixed version of the crate to avoid blocking on the bug fix getting merged.