Developers can disable Polonius Alpha and use the secure NLL borrow checker by passing -Zpolonius=off to rustc , utilizing RUSTFLAGS=-Zpolonius=off, or together with the next in a challenge’s .cargo/config.toml configuration file:
[target.x86_64-unknown-linux-gnu]
rustflags = ["-Zpolonius=off"]The Polonius borrow checker has been within the works since 2018. In 2023, a brand new formulation of a the Polonius borrow checker was proposed that required a minimal re-architecture of the present NLL (non-lexical lifetime) implementation and might be prolonged to permit extra sound code to compile, in accordance with Huey. Stabilization of that implementation has been delayed till now.
The borrow checker is a part of the Rust compiler that enforces strict guidelines on references, or borrowing. These embody making certain that every one variables are initialized earlier than they’re used, that the identical worth isn’t moved twice, {that a} worth isn’t moved whereas it’s borrowed, that a spot isn’t accessed whereas it’s mutably borrowed (besides via the reference), and that a spot isn’t mutated whereas it’s immutably borrowed, in accordance with the Rust documentation.
