Implementing Sub trait for slices

Question

Is it possible to implement the std::ops::Sub trait for slices in Rust? And if so how would I do that?

I tried the following:

use std::ops::Sub;

impl <'a, 'b, T> Sub<&'a [T]> for &'b [T] {
    type Output = Vec<T>;
    fn sub(self, rhs: &[T]) -> Vec<T> {
        difference(self, rhs)
    }
}

with difference having the signature:

difference<T: PartialEq + Copy>(xs: &[T], ys: &[T]) -> Vec<T>

compiling it results in the following error message:

error: type parameter `T` must be used as the type parameter for some local type 
    (e.g. `MyStruct<T>`); only traits defined in the current crate 
    can be implemented for a type parameter [E0210]
impl <'a, 'b, T> Sub<&'a [T]> for &'b [T] {
^

running then rust --explain E0210 to get further information I can kinda understand the problem, but I am confused about how the syntax would look like when using the struct MyType<T>(T); workaround described in the detailed explanation.

In difference to the question found How do I implement a trait I don't own for a type I don't own? my problem is I do not want this for vector types, but for slice types for which the syntax seems to be different enough that this answer is not really helpful.

It doesn't matter that it's a slice or a vec or a hashmap or a string or ...; if the trait and type aren't owned by you, you can't implement one for the other. — Shepmaster, Jun 24 '16 at 16:20
so the accepted answer for a possible workaround by wrapping the types in a new struct type in "How do I implement a trait I don't own for a type I don't own?" is wrong? — Alexander Battisti, Jun 24 '16 at 16:56
I don't understand how that conclusion was arrived at. Wrapping one type in another (the *newtype* pattern) means that *you own the wrapping type*. You can implement a trait you don't own for a type you do own. — Shepmaster, Jun 24 '16 at 17:01
My question is about syntax only. How does the signature for the trait implementation look, when using the new type pattern for wrapping a slice type in the context of wanting to implement the Sub trait. — Alexander Battisti, Jun 24 '16 at 17:21
Interesting - this question, as currently written, does not make that very clear. I would encourage you to ask a new question along the lines of "How do I create a newtype for a slice". Feel free to include the context from this question ("In order to implement `Sub` ..."). Make sure you include your attempt(s) at getting the syntax to work. I'm sure that question will get answered quickly. — Shepmaster, Jun 24 '16 at 17:27

Implementing Sub trait for slices

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