[vlovich123]

And yet modern optimizers don’t actually seem to have a problem with a transformation like that as you must know. Try list.iter().filter(|x| x>5).count() in Rust

And yes, Rust doesn’t have an effect system yet, but others have mentioned Haskell and how it handles tracing and logging and the limitations of effect systems interplaying with such things.

[jorkadeen]

It was a simple example; whether a specific optimization applies is very tricky. We have to look at the details. When can Rust move or eliminate a binder? Does Rust support automatic parallelization? What happens if you use unsafe blocks to lie to their type and ownership system? I think many of the same issues will surface.

To be me, the interesting question is: What happens when you lie to the type (and effect or ownership) system?

[vlovich123]

> Does Rust support automatic parallelization

No, and there's no indication that automatic parallelization is at all worth the effort vs having the author explicitly annotate which things need parallelization (e.g. Rayon is drop-in for many tasks where you know you'll need it). Otherwise you're at the mercy of heuristics baked into the language which in practice never work out well and also slow down the non multithreaded use-cases.

> To be me, the interesting question is: What happens when you lie to the type (and effect or ownership) system?

As others have said, just having the print get elided if the operation gets optimized out would be fine. That's what Haskell does. It's a weird choice to look at the challenges of effect systems and conclude the effect system idea is perfect it's the programmers who are wrong and not that the effect system has gaps that can't be addressed and solve it in other less surprising ways.