It is obviously has a lot of potential to be very fast.
It even does pretty good on DX. There is no borrow checker to fight. Algorithms that need indices in Rust are strongly typed references in Goose. Generally pleasant easy to read and write code.
The biggest thing against DX may be exactly where performance comes from: you need to think a bit on where to store your data :)
Where is the behavior specified?
> Goose: my latest programming language. Safer, faster and less memory than Rust/C++ for algorithms where tightly packed, flat data structures matter.
> It can represent more kinds of data structures as flat, pointer-free bytes than any language I know.
https://xitter.cf/wvo/status/2107979660558766351
So one way to answer might be: how often do you reach for unsafe when using Rust? If you don't I guess Rust is safer. If you do… it gets trickier.
As for UB, I guess you could try looking through the spec and/or the reference? Like, the code is mostly generated by Claude after WvO wrote a specification. If it were anyone else I'd be worried, but given WvO's cv I actually suspect that means the spec leaves basically no ambiguity.
However, Goose compiles to C. Does that by definition mean UB sneaks in, or is there a "UB free" C subset? I don't write C, so I don't really know.
UB in C potentially destroys the universe so C programmers do their best to avoid it. A backend that generates C code is a lot more easily constrained than arbitrary manual code. While it's conceivable that a C backend could produce UB code, it would be a severe bug and isn't likely. It most certainly isn't "by definition" ... that suggests some serious conceptual error.
The complete omission of UB in the README could be one of two things. Either that the topic is not important or that it is considered a given and not worth mentioning.
Note also the fact that e.g. array indexing has bounds checks without escape hatches for the programmer, but the compiler can elide quite a few of them, and the language has tools to help the programmer write code that is guaranteed to be check-free.
I think that suggests the ambition is to compete with Rust in the domain of combining safety with not compromising on performance.