Rust 1.73: What's New, Release History & Support Lifecycle

What Is New in Rust 1.73

How have panic messages changed in Rust 1.73?

Panic output no longer wraps the message in quotes and places the message on its own line.

This matters if your logs contain long or multi-line panic strings, because the new layout is easier to scan.

fn main() {
    let file = "ferris.txt";
    panic!("oh no! {file:?} not found!");
}

Running the program now prints:

thread 'main' panicked at src/main.rs:3:5:
oh no! "ferris.txt" not found!

What new thread-local APIs does Rust 1.73 provide?

The `LocalKey` type now exposes `get`, `set`, `take`, and `replace` methods directly.

This reduces boilerplate and avoids the extra initialization that the old `with` closure performed.

thread_local! {
    static THINGS: std::cell::Cell> = std::cell::Cell::new(Vec::new());
}

fn demo() {
    // old style
    THINGS.with(|c| c.set(vec![1, 2, 3]));
    // new style
    THINGS.set(vec![1, 2, 3]);

    // old style
    let v = THINGS.with(|c| c.take());
    // new style
    let v: Vec = THINGS.take();
}

Which APIs are now usable in const contexts as of Rust 1.73?

A handful of standard library functions have been stabilized for const evaluation.

This matters for embedded and compile-time computation because you can now call these functions inside `const fn` or const blocks.

Typical usage looks like:

const fn compute() -> usize {
    // call to a newly const-stabilized API
    std::mem::size_of::<[u8; 32]>()
}