How to Use Type-Level Programming in Rust

Rust does not have true type-level programming like Haskell; instead, it uses Generics, Traits, and Lifetimes to enforce constraints at compile time. You define generic types and implement traits to create reusable, type-safe abstractions that the compiler validates before execution.

struct ImportantExcerpt<'a> {
    part: &'a str,
}

impl<'a> ImportantExcerpt<'a> {
    fn level(&self) -> i32 {
        3
    }
}

fn main() {
    let novel = String::from("Call me Ishmael.");
    let first_sentence = novel.split('.').next().unwrap();
    let i = ImportantExcerpt { part: first_sentence };
    println!("Level: {}", i.level());
}

Type-level programming in Rust means using the compiler to check your code's logic before you run it, rather than waiting for errors during execution. You define flexible templates called generics and rules called traits to ensure data is used correctly. Think of it like a strict architect who checks your blueprints for safety violations before you ever lay a single brick.