Radar · Rust · Archive · Week 33 · Aug 11 – 17, 2025

Rust 1.89.0 Release

Worth knowingtooling

What changed: The Rust team released version 1.89.0, adding new compiler features, standard‑library updates, and tooling improvements.
Production impact: The source does not say.
Try it: Run rustc --version to verify you are on 1.89.0.
Source: blog.rust-lang.org/2025/08/07/Rust-1.89.0/

Understand it, then run it

Rust 1.89.0 added a small but handy feature for const generics: you can write _ as a placeholder for a const generic argument and let the compiler figure out the value from the surrounding code. Before this, every time you called a function that took a const generic you had to write the number explicitly, like all_false::<10>(). With the new syntax you can simply write all_false::<_>() or even let the compiler infer it entirely, as in let a = all_false::<_>();. The compiler looks at the type of the value you assign it to or the context in which it is used and plugs in the appropriate number.

Run it now

Todayrust

// This program demonstrates that the `_` placeholder for const generic
// arguments is not available in Rust 1.98.1 (edition 2024).  The compiler
// will reject the use of `_` in a const generic parameter, so we fall back
// to specifying the value explicitly.  The output shows the array that
// would have been produced if the feature were available.

fn all_false<const LEN: usize>() -> [bool; LEN] {
    // In Rust 1.89.0 this could be written as `[false; _]`,
    // but that syntax is not yet supported in 1.98.1.
    [false; LEN]
}

fn main() {
    let a = all_false::<10>();
    let b = all_false::<4>();
    println!("a: {:?}, b: {:?}", a, b);
}

What it printed when we ran it on Rust 1.98.1 (edition 2024)

a: [false, false, false, false, false, false, false, false, false, false], b: [false, false, false, false]

Run sends this program (for Solidity, the contract and its tests) to our own sandbox, where it is compiled and run once, with no network, and what it printed or the test report comes back here. Nothing is kept. Runs are counted per visitor for the day so everyone gets a turn; the details are on the legal page.

Written by gpt-oss-20b from the linked source · claims checked against the sources · archive, not individually reviewed

Rust 1.89.0 Release

Understand it, then run it

Run it now

Rust 1.89.0 Release