Pin Struct

Pinning for self-referential types

Pin Basics

use std::pin::Pin;
use std::marker::PhantomPinned;

fn main() {
    // Pin prevents moving a value
    // Needed for self-referential types (e.g., async futures)

    println!("=== What is Pin? ===");
    println!("Pin<P> wraps a pointer P (e.g., &mut T, Box<T>)");
    println!("It guarantees the pointee won't move");
    println!();

    println!("=== Why Pin? ===");
    println!("Self-referential structs have pointers to themselves");
    println!("If moved, internal pointers become invalid");
    println!("Async blocks can be self-referential");
    println!();

    // Unpin types - safe to move even when pinned
    let mut x = 42;
    let pinned = Pin::new(&mut x);
    println!("i32 is Unpin: can be moved freely");
    println!("Pinned value: {}", *pinned);
}