Wrap a primitive in a tuple struct to give it a distinct type identity at the type level — without runtime cost. Replaces "is this number a UserId or a PostId?" bugs.
Rust
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
struct UserId(u64);
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
struct PostId(u64);
fn delete_user(id: UserId) {
println!("deleting user {}", id.0);
}
fn main() {
let u = UserId(42);
let p = PostId(99);
delete_user(u); // ✓
// delete_user(p); // ❌ mismatched types: expected UserId
// delete_user(42); // ❌ expected UserId, got integer
}Save your own code snippets
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