This exists, and is called static analysis. There are tools that can analyze code paths and build a theoretical model of lifetimes throughout a problem. Mind y

This exists, and is called static analysis. There are tools that can analyze code paths and build a theoretical model of lifetimes throughout a problem. Mind you, I don't know the formal theory enough to say whether you can build a static analysis tool that is actually capable of doing what Rust's lifetimes accomplish in a provably complete manner. Maybe someone else can chime in here. However, there are other disadvantages to this approach. Not having it in the language means everyone working on the program has to be using the exact same static analysis tools, and they have to be using it on the entire program, including libraries. Rust ensures that the lifetimes are enforced consistently, since there's only one possible engine enforcing them. There are some very impressive code analysis tools used in the industry (with C and C++, in particular), but far as I know, they are all commercial and fairly expensive. As far as I know, open source tools like Valgrind are not powerful enough.