Trait Bounds on Generics

// Copyright 2025 Google LLC
// SPDX-License-Identifier: Apache-2.0

use std::fmt::Display;

fn print_with_length<T: Display>(item: T) {
    println!("Item: {}", item);
    println!("Length: {}", item.to_string().len());
}

fn main() {
    let number = 42;
    let text = "Hello, Rust!";

    print_with_length(number); // Works with integers
    print_with_length(text); // Works with strings
}

Traits are most commonly used as bounds on generic type parameters for a function or method.

Without a trait bound on a generic type parameter, we don’t have access to any behavior to write functions and methods with.

Trait bounds allow us to specify the minimum viable behavior of a type for it to work in generic code.

ref:

https://doc.rust-lang.org/reference/trait-bounds.html