If a language that claims to be security focused is easily able to express constructs that human minds find barely comprehensible, or worse, then this is itself arguably a security issue: it's impossible to check the correctness of logic that is incomprehensible.
What's the threat model? If you're reviewing untrusted or security-critical code and it's incomprehensible, for any reason, then it's a reject.
Syntax alone can't stop sufficiently determined fools. Lisp has famously simple syntax, but can easily be written in an incomprehensible way. Assembly languages have very restrictive syntax, but that doesn't make them easy to comprehend.
Rust already has a pretty strong type system and tons of lints that stop more bad programs than many other languages.
Many modern language designers focus on shaping expressibility rather than providing the maximum possible flexibility because their designers learned from C, Lisp and other languages that made mistakes. Examples lamguages are Java, C#, D, Go... some arguably with more success than others. But language design that gave ultimate expressive power to the the programmer is a relic of the past.
"Expressibility" and "expressive power" are vague and subjective, so it's not clear what you mean.
I suppose you object to orthogonality in the syntax? Golang and Java definitely lack it.
But you also mention C in the context of "maximum possible flexibility"? There's barely any in there. I can only agree it has mistakes for others to learn from.
There's hardly any commonality between the languages you list. C# keeps adding clever syntax sugar, while Go officially gave up on removing its noisiest boilerplate.
D has fun stuff like UFCS, template metaprogramming, string mixins, lambdas — enough to create "incomprehensible" code if you wanted to.
You're talking about modern languages vs relics of the past, but all the languages you mention are older than Rust.
Have you ever seen submissions to IOCCC or Underhanded C Code Contest? That is what too much syntactic flexibility looks like (if taken to the extreme).
If you want your code to be secure, you need it to be correct. And in order for it to be correct, it needs to be comprehensible first. And that requires syntax and semantics devoid of weird surprises.
Eh, I'm not sure I agree here. This feels sort of along the lines of, "well C is safe because someone can review your code and reject it if you try to dereference a possibly-NULL pointer".
The point of a language that is "safe" along some axes is that it makes those unsafe things impossible to represent, either by omitting an unsafe feature entirely, or making it a compile-time error to do unsafe/unsound things.
I will admit that this is something of a grey area, since we're talking about logic errors here and not (for example) memory-safety bugs. It's a bit muddier.
In general, though, I do agree that people should write code that is reasonable to read, and if a reviewer thinks some code in a PR is incomprehensible, they should reject it.
I think these situations are very different, because Weird Rust affects only weird code, while unsafety of C affects regular C code.
The difficulty in reviewing pointer dereferences is in reasoning about potential program's states and necessary preconditions, which C won't do for you. You can have neatly written C using very simple syntax, and still have no idea if it's safe or not. Solving that lack of clarity requires much than syntax-level changes.
OTOH the Weird Rust examples are not a problem you get in your own code. It's a local syntax problem, and it doesn't require complex whole-program reasoning. The stakes are also lower, because you still have the same safety checks, type checks, automatic memory management, immutability. The compiler aggressively warns about unreachable code and unused/unread variables, so it's not easy to write undetected Weird code.
Rust tried having Underhanded Code Contest, but it has been very Underwhelming.
"Memory safety" is an aspect of computer security. And security is the first listed value in rust's mission statement.
Rust is not written as a pure expression based language. And as we all know very well from the experience with C and JS, any unexpected and weird looking code has the potential to hide great harm. Allowing programmers to stray too much from expected idioms is dangerous.
I think you're looking at it a little backward. Or rather, with superset/subset confusion. Rust can say "we care about memory safety" without being security-focused. But Rust cannot say "we are security-focused" without also caring about memory safety.
Being security-focused requires you to care about a laundry list of things, including memory safety. But on its own, caring about memory safety just means... you care about memory safety.
"never" is an easily comprehensible concept once you start asking the right questions.
But also, all examples in TFA are very artificial convoluted code. Meaning that you can write things like these just like you can write something like &&&...x - but why would you? Actual real-world uses of this feature are all quite readable.
It is a critique of macros. 500 lines of Common Lisp replaces 50,000 lines of C++ but those 500 lines make no sense at all the first time you see them.
