I find Rust simpler, more concise, and nearly no footguns.
Edit, I didn’t see your Java comment:
> I wouldn't say that Rust's safer than Java either.
Here’s why it is safer: It has the same set of guarantees about memory safety as Java. In terms of concurrency, it is safer because of the single mutable reference guarantees across threads, enabled by a better type system. The type system is stronger, which allows for more details about code to be put into types, like algebraic data types of Rust, without the limitations of Java’s non-generic enums.
And the big one: no bare nulls allowed. This reduces a huge set of logic errors. Now Java is getting Value types in a future release which will allow for a true Option type in Java, ie one that cannot itself be null, the other points still stand.
On top of that, in large applications the GC can become an Achilles Heel, where it eventually pauses the application with dire consequences. Rust of course has no GC. And a great side effect of this is that Drop (java Finalizers) actually work in Rust, which is amazing.
Basically for these reasons, Rust is safer than Java.
My personal opinion is that they have similar complexity, but in general Rust decides to clearly define behaviour as much as possible and fail fast, preferably at compile time. This can be seen when comparing features: memory management is there (supported by the borrow checker), smart pointers are there, references & pointers are there, generics are there (even if not exactly the same), integer and floating point handling are there, concurrency is there (compile-time checking is nice), macros are there (albeit different and perhaps less error prone), string types are more complex than cpp, enums are more complex (but also more powerful), operator overloading is there, iterators are clearly more complex (and the functional aspects in general), etc.
So the average programmer will have to learn a similar amount of concepts or even more in Rust's case.
Where Rust is indeed simpler is error handling and building.
--- I figured you would bring up concurrency, and while Rust's compile-time verification is really nice, Java also has a simpler form in threading annotations. Additionally, I believe it's rare to use such low-level primitives in Java.
Nulls (and type system holes in general) are a correctness issue, not a safety issue, unless we want to argue that all bugs are safety issues.
GC pauses are a performance issue, as you already know.
Saying that Rust threading is safer than Java's is technically correct and Rust is probably a bit safer than Java because of that, but it's hard to argue that Rust should be chosen for a project because of that (this is the whole point of saying X is safer than Y). Java is super-simple to learn compared to Rust.
I just wanted to make it clear how and why I've formed that opinion.
> unless we want to argue that all bugs are safety issues
Yes, I can definitely be accused of expanding the definition of safety to include all things that cause programs to crash in horrible ways. I look at it as differing levels of guarantees the language makes for you, and Rust makes many more at compile time than others. This adds to the learning curve you mention, is it worth it? Completely depends on if you see those guarantees as valuable.
C++ as a language is a lot more complicated. It has a lot of features with weird corner cases that interact in unfortunate ways.
> And I wouldn't say that Rust's safer than Java either.
Depends on what you mean with safe. If you mean memory safe, then they are about as safe. Rust has fewer runtime failures due to concurrency and null pointers though.
Honestly, after hating C++ for years, trying to use Rust made me appreciate more about C++. I wish someone would make a language which took the best parts of both.
We'll just have to agree to disagree, because having the compiler watch my back and preemptively guard against unforeseen pitfalls is about the warmest comfort I could ask for. :P
And yes, I meant memory safety.
And I wouldn't say that Rust's safer than Java either. Memory access errors are basically non-existant in Java and it has quite robust concurrency primitives and libraries.