Hello,
I’m currently trying to solve coding puzzles from Advent of Code (i’m not gonna ask for a solution here 
), using Rust so i can learn more about the language. For now, even if it’s more verbose than, say, Python, i really enjoy it so i’ll continue.
And now, on a given problem, i thought i could go further using Rust and use generics in a more “advanced” way. I’m currently stuck on a pure Rust problem. Consider this code:
use std::ops::Add;
pub struct Remote<T> {
x: T,
}
pub struct Local<S> {
x: S,
}
pub struct Adder<T> {
local: Local<T>
}
impl<I: Add> Adder<I> {
pub fn add(&self, r: Remote<I>) -> I {
self.local.x + r.x
}
}
fn main() {
let adder: Adder<u64> = Adder{local: Local{x:1}};
let remote: Remote<u64> = Remote{x:2};
adder.add(remote);
}
Before even trying to compile, i smelled that something could go wrong with this. I want to add “types” S and T… but they aren’t “linked” together in any way… but as i’m not sure about what the compiler is telling me
error[E0308]: mismatched types
--> src/main.rs:17:9
|
16 | pub fn add(&self, r: Remote<I>) -> I {
| - expected `I` because of return type
17 | self.local.x + r.x
| ^^^^^^^^^^^^^^^^^^ expected type parameter, found associated type
|
= note: expected type `I`
found type `<I as std::ops::Add>::Output`
So aaah… associated type? I tried to do some messy stuff with a second type parameter (named C) on Adder, using PhantomData to actually do something with it so the compiler doesn’t yell at me, and using r: Remote<C> but it doesn’t work any more.
Suddenly I remembered that i could use C=Remote<I> but then the compiler say something like “deprecated” so it’s a no go either.
How could i achieve to get the same type for Remote and Local?
Thanks
