Valen's Memory Safety: A New Kind of Borrow Checking

Valen's group-borrowing checker aims to stop use-after-free with fewer restrictions than Rust-style borrow checking.

A Valen blog post describes a relaxed borrow checker based on Nick Smith's group-borrowing design. The compiler tracks where references point and rejects use-after-free at compile time while allowing patterns Rust typically rejects, including multiple mutable aliases. The design is meant to interoperate with Rust and to combine with Vale-style reference counting and generational references. Related languages including Google's Carbon, Ante, and Fang have explored similar ideas.