A new way to think about borrow checking (in reverse)

Valen, an experimental programming language, introduces an unconventional borrow checker that operates in reverse—walking through functions backwards from the final statement to the beginning—to verify memory safety, a novel approach not previously used in memory safety checking. This backward iteration allows Valen's borrow checker to make shared-mutable borrowing optional and enable memory-safe interoperability with Rust functions, departing from traditional shared-xor-mutable borrow checking models like Rust's.