[pkolaczk]

> there are tools that don't require manual memory management or being pedantic about the different types of strings. You could just use Go, Java, Haskell, Python, etc.

1. Rust doesn't force you to do manual memory management. Rust memory management is automatic by default and only if you really, really want to, you can do it manually.

2. Memory is not the only resource. The GCs in languages you listed only solve the memory management problem, but regarding the other types of resources, their ergonomics are often worse than C - you have to remember to close the resources manually and you get virtually no help from the compiler.

3. None of the listed languages address problems related to concurrency, e.g. data races. Ok, Haskell kinda avoids the problem by imposing other restrictions - by not allowing mutation / side effects ;)

4. Rust offers way better tools for building high level abstractions than Go, Python and Java. It has set a very high bar with algebraic data types, pattern matching, traits/generics and macros.

[kaba0]

1. Rust does manual memory management. It has some syntactic sugar for it in the form of a compiler-enforced RAII, but that is still manual memory management for all practical purposes. A good distinction to make is whether low-level, memory/ownership details leak into public APIs. This is trivially true for Rust, while is not true of managed languages.

3. Rust only addresses problems related to data races, not as an example. All the other race conditions are still on the table. It is a good thing to have, but I think they are the least problematic, and easiest to solve part of concurrency issues.

4. All of these have been known for like 3 decades. There are plenty of managed languages with these, ML, OCaml, Haskell, Scala. But I think your claim is subjective at best.

[pkolaczk]

> It has some syntactic sugar for it in the form of a compiler-enforced RAII, but that is still manual memory management for all practical purposes.

Then you've got a different definition of "manual" than mine. Manual means that developer has to insert calls to allocate / deallocate memory and that the developer is responsible for proving the correctness of those calls. Automated means those calls are done by the runtime or by the compiler automatically, and the compiler makes sure they are correct. In case of Rust, those calls are inserted automatically by the compiler.

> memory/ownership details leak into public APIs

The fact that ownership is a part of public API is a good thing, similarly how it is a good thing to specify an argument is an integer and not a string.

> There are plenty of managed languages with these, ML, OCaml, Haskell, Scala.

I referred to the ones mentioned in the above comment, which mentuoned Java/Go/Python. Haskell/Scala/Ocaml/ML are quite niche even compared to Rust these days.

But even though Haskell / Scala might get close on some type-system features, they don't offer similar experience as Rust in other areas. Haskell is more restrictive in terms of managing state than borrow-checker, and Scala tooling / compile times has been always horrible.

> Rust only addresses problems related to data races, not as an example. All the other race conditions are still on the table.

This is like saying a statically typed language doesn't stop you from putting a string telephone number into a string surname field. Sure it doesn't. But despite that, the value of static types is hard to overestimate.

In practice, the borrow checking + RAII + Send/Sync rules can be used to make the other types of concurrency problems very unlikely by properly modeling the APIs. Sure, no language can protect from all concurrency problems in general, but at least Rust gives you some good tools. For instance it is trivial to forbid concurrent access to something that shouldn't be accessed concurrently and let the compiler enforce that. Now try enforcing that in your "business oriented language of choice". In my experience the majority of concurrency related problems in real large-scale software development happen when some code not designed to handle concurrency accidentally becomes executed concurrently because developers don't realize something is shared and mutated at the same time. Another type of common issue is with communicating concurrent threads of execution, when one sends a message but the receiver is not there on the other end because of premature exit e.g. due to error, leading to a deadlock. Rust protects from those really well.

[kaba0]

> The fact that ownership is a part of public API is a good thing

A libraries next version which switches up some internal representations memory handling should ideally not mess up your application, but it also mandates a higher refactor rate when you are only working within your application’s boundaries. These are worthwhile tradeoffs for the niche rust is targeting, but not for every use case.

I’m not saying Rust is a bad language, I really like using it for its intended niche of complex applications where absolute control is needed, like a browser engine. But it is not a panacea and I would definitely not choose it for a CRUD webapp.

[pkolaczk]

> A libraries next version which switches up some internal representations memory handling should ideally not mess up your application

It doesn't have to because internal memory representation can and should be abstracted out, and Rust gives a plethora of tools to do that.

Your argument works against against static typing in general. The next version changes the address representation from String to Address (in managed language) and messes up your app. That's the same thing.

[foldr]

If version 1 of your library has a function that returns a reference to T, then that constrains your choices of implementation for the underlying data structures containing Ts more than they would be constrained in a garbage-collected language. So unless there is to be a ban on functions returning simple references, Rust is always going to be a little less flexible in this respect. That is fine and expected given the overall design goals of the language, but there's no point pretending that it's not the case.

The simplest concrete example, I guess, would be a function that returns &'str. There are plenty of Rust APIs out that have functions with this type signature.

[pkolaczk]

> If version 1 of your library has a function that returns a reference to T, then that constrains your choices of implementation for the underlying data structures containing Ts more than they would be constrained in a garbage-collected language

This is IMHO a good thing. If it returns a reference to T, it means it still owns it and allows only temporary usage of it. This is semantics of ownership and does not have anything to do with memory management. If you wanted to allow sharing for unspecified lifetime, sure, you can. There is Rc/Arc.

I've fixed plenty of bugs in code written in managed languages, where a reference to T was handed out from a library (because there is no other choice - everything is a reference) and then someone stored it for longer than it was valid, leading to a logical equivalent of use-after-free.

E.g. get an entity object managed by Hibernate. Pass it up outside of the context of Hibernate session. It will likely blow up because the object references a session that's now closed. Rust ownership model would prevent exactly that problem.

I find this "flexibility" of managed languages actually a problem in large codebases, similarly how flexibility of goto is universally considered bad. It severely hinders maintainablity. It allows to pass references freely and create implicit, complex, often cyclic, reference graphs which are very hard to reason about.

In my Rust code 99% of objects don't need shared ownership. But managed languages make shared ownership the default, optimizing for the edge-case.

BTW, your statement can be rephrased to: "If version 1 of your library has a function that accepts a reference to T, then that constrains your choices of values of T more than it would be constrained in a dynamically typed language."

You may say that you can use Any / Variant / Object in a statically typed language to overcome that limitation. True, and similarly you can use Rc/Arc/Copy types in Rust.

This is all the same thing. It just takes static typing to the next level. Not only it allows to express constraints on values, but it also allows to express constraints on time they can be used.

[kaba0]

> Your argument works against against static typing in general

I don’t think this argument works. Ad absurdum a very strong type system would even specify the implementation itself, making any change breaking — is that good? No, it isn’t as the useful property of the type system is no longer there. I don’t agree that this usefulness line is behind “ownership annotations” — that’s what you would have to convince me of.