Generics: Parametric Polymorphism

Generics allow functions, structs, and enums to operate on parametric types instead of single concrete types.

Basic Usage & Constraints

You can restrict generic parameters to types implementing specific traits using trait bounds (: TraitName):

use std::fmt::Debug;

fn log_action<T: Debug>(action: T) {
    println!("System Event: {:?}", action);
}

log_action(100); // works because i32 implements Debug
log_action("HookTriggered"); // works because &str implements Debug

Compile-Time Monomorphization

How does Rust perform generics at runtime? It uses Monomorphization. At compile time, the compiler looks at all concrete arguments used to invoke log_action. It duplicates the code, replacing T with the exact types used.

• Result: No dynamic casting, no interface lookup pointers.
• Performance: Direct static calls. Complete zero-overhead performance, matching hand-written separate functions.