Valen's borrow checker permits mutable aliases by tracking where references point
Evan Ovadia's experimental language builds on Nick Smith's group-borrowing proposal, with Rust interoperability as a design target.
By RuntimeWire Staff · Published · Updated
Primary source: Evan Ovadia
Why it matters
Valen is testing whether compile-time safety can accommodate mutable aliasing without dangling references, a tradeoff with implications for systems languages and Rust interoperability. Its prototype and patched-rustc requirement make this an early design, not a production alternative to Rust.
Evan Ovadia published a new account of Valen's borrow checker on October 11th, describing a compiler design that allows multiple references to the same object to read and write while tracking whether those references could become invalid. The proposal, called group borrowing, shifts the safety check from forbidding certain combinations of references to recording where each reference points and what an operation might invalidate.…