Giooschi

Sorry, by looking more into it I realized webview is actually a different thing than what I was thinking about.

This would be so good. As someone who fully switched to Firefox on Android I hate that chrome webview is a thing.

Why does that bother you? There's also a Firefox Webview you can use system-wide. I think only Google apps insists on opening Chrome's webview.

banning patients

Did you mean patents?

Do you apply the same reasoning for software that use javascript, the JVM, the CLR or some other kind of VM?

These are server CPUs, not something you wanna put in your laptop or desktop.

What? You can easily escape from it if there are better alternatives you can use.

So there is no general escape hatch.

Pointing at one language and saying it is not easy to code like it is another language is a pointless argument.

I'm not arguing that it is easier to code in C# than in Rust, just that this particular escape hatch is possible in C# and not in Rust. It's just an observation.

They all differ for good reasons and as long as you can solve similar problems in both, even if in different ways then what does it matter that you cannot do it in the same way?

It does not really matter, but does it have to?

This is a kind of stupid example, but imagine you have to implement some external trait (e.g. in order to work with some dependency) with the following shape:

trait Foo {
    fn foo(&self, i: usize) -> &Bar;
}

Which is not too unreasonable, for example it's very similar to the stdlib's Index. In order to implement this trait you must return a reference, you can't return e.g. a Cow or an Arc. The fact that it takes a parameter means there might not even be one single value it has to return, so you can't even cache that inside of self with e.g. LazyLock.

Of course I'm not saying I would try to reach for an escape hatch if I had to do something like this. I would first try to see if this is an intrinsic problem in my code, or if maybe I can change the crate I'm working with to be more permissible. That is, I would try to look for proper solutions first, though Cow might not always work for that.

You dont write code like this in rust.

I perfectly agree, that would be horrible code! I would generally try to restructure my code, making it better fit the actual lifetimes of the data I'm working with. The point in the article is that you can't really escape from this. I'm not arguing this is a real problem, and I don't think the article is neither, just pointing out that this is something you can easily do in C# and not in Rust. It's just a difference between the two languages.

I can agree that the example function is not the best usecase. But the point still stand that there's no realistic escape hatch from lifetimes and memory management in Rust.

Cow does not work when you are actually required to return a reference, e.g. if you're working with some other crate that requires that. Cow also has some more strict requirements on reborrows (i.e. you can reborrow a &'short &'long T to a &'long T, but you can only reborrow a &'short Cow<'long, T> to a &'short T).

LazyLock can solve very specific issues like static, but is not a general escape hatch. Again, the example is not the best to showcase this, but imagine if you have to perform this operation for an unknown amount of runtime values. LazyLock will only work for the very first one.

It's a very different kind of borrow checking than Rust's. For example there's no mutability xor sharing checking, because mutability cannot invalidate memory (there's still a GC in C# after all!). As such, Rust's NLL (which are available in the 2015 edition too btw) don't really make sense in C#.

(Note that I'm not the article author)

In this example, you could have just made a constant with value 0 and returned a reference to that. It would also have a 'static lifetime and there would be no leaking.

I believe the intention was to demonstrate something that works with runtime values too, and a constant 0 does not.

Btw you can just write &0 to do what you proposed, there's no need for an explicit constant/static.

write only medium

I guess you meant "write once"?

Anyway, this won't prevent attacks that somehow swap the CD being read, or the backend logic for where to read the data from.