scoped_static

Lift references into 'static safely — at runtime.

scoped_static allows temporarily extending a reference’s lifetime to 'static using runtime safety checks. This enables you to safely spawn asynchronous tasks, threads, or other 'static contexts without running into borrow checker limitations — while still avoiding undefined behavior.

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Motivation

Rust’s lifetime system ensures safety at compile time, but sometimes you need to move a non-'static reference into an async task or thread:

#[tokio::main]
async fn main() {
    let concrete_value = Box::new(1.0);
    let ref_value = &concrete_value; // This is does not live long enough (not 'static)
    tokio::spawn(async move {
        let value = **ref_value + 1.0;
        assert_eq!(value, 2.0);
    })
    .await
    .unwrap();
}

This fails because the reference to ref_value isn’t 'static.

scoped_static solves this by allowing you to lift a reference to 'static under the protection of a scope guard that enforces correct drop order at runtime.

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Example

use scoped_static::{scoped, ScopedGuard};

#[tokio::main]
async fn main() {
    let value = Box::new(1.0);
    let ref_value = &value;
    // `guard` ensures no derived "lifted" values exist when dropped.
    // The type is `&mut ScopedGuard<'_, Box<f64>>`
    let guard = scoped!(ref_value);
    // `lifted` holds a `'static` reference to `'ref_value`
    // The type is `Scoped<Box<f64>>`
    let lifted = guard.lift();
    tokio::spawn(async move {
        // `lifted` moved here
        let value = **lifted + 1.0;
        assert_eq!(value, 2.0);
        // `lifted` dropped
    })
    .await
    .unwrap();
    // Forgetting has no effect since `guard` is a reference
    std::mem::forget(guard); // SAFE
   // `guard` dropped
}

See ScopedGuard and ScopedPinGuard for more info.