You can only define an inherent implementation for a type in the same crate where the type was defined. For example, an impl block as below is not allowed since Vec is defined in the standard library:

impl Vec<u8> { } // error

To fix this problem, you can do either of these things:

• define a trait that has the desired associated functions/types/constants and implement the trait for the type in question
• define a new type wrapping the type and define an implementation on the new type

Note that using the type keyword does not work here because type only introduces a type alias:

type Bytes = Vec<u8>;

impl Bytes { } // error, same as above