From Linearity to Borrowing

Explore the theoretical foundations of borrowing mechanisms in programming languages through this 16-minute conference presentation from OOPSLA 2025. Delve into how linear type systems can statically ensure correct resource management while examining the challenges they present in practical programming scenarios. Learn how borrowing, as exemplified in Rust, addresses these limitations by temporarily disabling certain resource permissions while enabling structural permissions, allowing programmers to work more efficiently without explicit resource threading. Follow the systematic development of the Borrow Calculus (BoCa), starting from a standard linear type system for safe manual memory management and progressively incorporating immutable borrows, lexical lifetimes, reborrowing, and mutable borrows. Understand the novel Borrow Logic (BoLo), a domain-specific separation logic designed specifically for reasoning about borrowing semantics. Discover how the semantic model guarantees program termination and freedom from memory leaks while proving semantic type soundness. Examine the robustness of the Borrow Logic framework through examples of syntactically ill-typed programs that maintain semantic safety by temporarily breaking and reestablishing invariants, providing insights into advanced type system design and formal verification techniques for resource management.