> Having to bear the cognitive burden of making the lifetime explicit in all of the code is a steep price to pay for the benefit of securing the small subset of the code that is actually complex enough to potentially cause a problem. I wouldn't mind having such a feature be optional though, so that you'd enable it for the most precarious parts, something like a safe{} block rather than unsafe{}.

It's obviously a learning curve burden but now that I use the language on a daily basis, it doesn't really slows me down. The thing is you don't often need to annotate the lifetimes by hand since the compiler elides the most common case. In practice, the time you need to do the annotation is often what you call «actually complex enough to potentially cause a problem».