Code shared from the Rust Playground

playground.rs

// ==========================================
// INCORRECT: Dyn-Incompatible Trait
// ==========================================
// Uncommenting this will cause a compilation error:
// "the trait `Processor` cannot be made into an object"
/*
trait Processor {
    // Error 1: Uses `Self` in return position
    fn duplicate(&self) -> Self;

    // Error 2: Has a generic type parameter `T`
    fn process_data<T>(&self, data: T);
}
*/

// ==========================================
// CORRECT: Dyn-Compatible Refactored Version
// ==========================================
use std::fmt::Debug;

trait Processor {
    // 1. Valid dynamic dispatch method
    fn name(&self) -> &str;

    // 2. Exempted via `where Self: Sized` (cannot be called via `dyn Processor`)
    fn _duplicate(&self) -> Self where Self: Sized;

    // 3. Generic requirement removed or replaced with a trait object (type erasure)
    fn process_data(&self, data: &dyn Debug);
}

struct AudioProcessor;

impl Processor for AudioProcessor {
    fn name(&self) -> &str {
        "AudioProcessor"
    }

    fn _duplicate(&self) -> Self {
        AudioProcessor
    }

    fn process_data(&self, data: &dyn Debug) {
        println!("Processing audio data: {:?}", data);
    }
}

fn run_processor(p: &dyn Processor) {
    println!("Running: {}", p.name());
    p.process_data(&42); // Passes concrete data via trait object reference
    
    // p._duplicate(); // ERROR: Cannot call because it requires `Self: Sized`
}

fn main() {
    let audio = AudioProcessor;
    run_processor(&audio);
}

Playground.toml

version = "1"