[masklinn]

In fact noting pretty much what you wrote in the first paragraph would improve it a lot: below the initial error message (above the expansion stuff) it could note

    requires that "i" implements Debug, but

    src/x/mod.rs:15 impl<T> Info for Buffer<T> {
    does not specify that T must be Debug

    hint: you can bound T to Debug:

        impl <T> Info for Buffer<T> where T: Debug {

    this means the code will only work with types which implements Debug, 
    but lets you use Debug operations in your methods

Worse, the rest of the error message gives completely the wrong direction for this error case, it gives an advice for a concrete type T, not for a generic one.