It's very nice language and not just because of the language features. The tooling is awesome and modern. Compiler errors are top class, cargo is a great package manager, rust-analyzer is a great LSP.
However, I think the way the language has implemented `async` is going to cause a riff in the usage. Because they didn't standardize the executors interface, you're essentially forced to using a single runtime (Tokio) since library developers would have to code for each runtime. Also, because of the async keyword, library developers would also have to make a different sync/async of each function they want to declare.
These are not small issues and will only continue to get worse as people are forced to choose one route, leaving others to use a different language.
Since all Rust programs have sync entrypoints, there is always some way to call async functions from sync functions. It's not like C# or Go where the async runtime is a singleton built deep into the language. You always have control of it.
In practice, if I'm doing anything with networking, I always end up wanting async, so I prefer to have the runtime and use spawn_blocking for sync APIs.
That's async calling sync. But if you're in sync and the only option is to call an async library because the author didn't want to make two versions then you have to pull in the async runtime as well.
Not everyone wants to pull in an async runtime just to run make a call to an API.
My whole point is async puts a huge burden on library authors that will force users to diverge in their approaches and that will ultimately hurt the community
> [B]ecause of the async keyword, library developers would also have to make a different sync/async of each function they want to declare.
This is a program with async in general, no? Go avoids this by just having everything be async, but that seems unsuitable for Rust since you won't have control over when your code executes and what thread it executes on, not a problem for applications but it would seem to rule out things like kernel modules and firmwares, as well as require every type to be Send + Sync (which ultimately means the language must be garbage collected).
In Python for example I've written async and sync versions of a library, and some magic testing that makes sure both implementations return the same results.
> These are not small issues and will only continue to get worse as people are forced to choose one route, leaving others to use a different language.
Honestly this doesn't seem like a problem to me. I think there's room for many languages in this world. Rust is a wonderful language but it isn't a "one true language." People should choose a different language if it suits them better. That's no more an indictment of Rust than it's an indictment of Python when I embed Rust in a web app - that's not a place where Python shines.
Sadly, I agree. It's a lot like C#'s quest against nullability: the feature was introduced too late into a stable design in a form that is obviously incomplete, tries too hard to maintain compatibility with existing code and fails.
I've never worked with C# so I need to look into that.
The one saving grace with Rust is if everyone decides to say "screw async" and just builds synchronous APIs, then we use something like [May](https://github.com/Xudong-Huang/may) for green threading.
It's not, but it's very good for writing system software. Modern C++ is also good, probably good enough for the majority of the cases, but Rust is there for you when you can't afford a GC and you must be absolutely right you're not introducing memory management errors.
If you're using modern C++ then you really have to be screwing up to introduce memory management errors. For 99% of programs high level (STL-based) types are sufficient, and if you really need to be allocating things yourself, then smart pointers and RAII make it pretty hard to mess up, unless you choose to circumvent the scope-based lifetime they provide and start doing things like ptr.release() instead.
To me C++ pretty well follows the "make simple things easy/safe, and hard things possible" philosophy. I'm glad this it still does support low level stuff, but the use cases for that are minimal and I do wish there was a compiler flag to reject full C backwards compatibility and only support a modern safe subset, so that projects could protect themselves from junior developers shooting themself in the foot.
Well, yeah, but that's not really a memory error - it's an error of not using mt-safe data structures for mt programming. It's no different than using int vs std::atomic<int> in an mt context.
It's a shame that C++ doesn't provide mt-safe versions of STL types in the standard library, although trivial to wrap them yourself (1 line of code per method, using std::lock_guard).
Are all Rust data types mt-safe? Does unsafe mode provide faster unprotected versions if you need those?
Yes, but not in the sense you probably think, given your second sentence:
> Does unsafe mode provide faster unprotected versions if you need those?
Some data types can be safely shared between threads, and some cannot. Rust checks at compile time if you try and use a non-thread safe data structure from multiple threads, and if you do, will give you an error. So in that sense, all of them are safe, yes.
You don’t use unsafe to get access to non-thread safe data structures, you may have both kinds, and the compiler checks you use them correctly.
Interesting. So I assume there are at least both basic and thread-safe versions of basic types like string/list/vector/map ?
Is there any provision for building your own thread-safe types (e.g. a structure composed of other types) out of non-thread-safe types and mutexes, and if so how does that work in terms of compile-time errors ?
Far from it. It's main selling point is that it's friendly.
I had C/C++ in college and spent most of my career in front-end.
In comparison to the Cs Rust at least tries to get out your way. Stuff generally compiles and when it doesn't, it tells you what might be wrong using human language.
I mean, it's the first time I've seen a compiler error start with "perhaps..." to tell you what steps could be taken to fix it.
It's great to have a compiler give useful diagnostics, but it has to be said that's mostly a function of the compiler vs language.
LLVM-based compilers such as the rust compiler and Clang (C++) tend to be way better than g++ in this regard, although Clang competition has forced g++ to be a little better in recent years.
It's got about the same hype that node or Go got, so it's not like you need a high level of perfection for that. Never mind that some of that is coming from a crowd I'm not too fond of.
Personally, I don't think it's worth all that just to avoid a garbage collector, but it's not like there are that many decent compile languages with GC currently on the hype train.
However, I think the way the language has implemented `async` is going to cause a riff in the usage. Because they didn't standardize the executors interface, you're essentially forced to using a single runtime (Tokio) since library developers would have to code for each runtime. Also, because of the async keyword, library developers would also have to make a different sync/async of each function they want to declare.
These are not small issues and will only continue to get worse as people are forced to choose one route, leaving others to use a different language.