made in gimp, with <3
Context for actual rust programmers
I was having massive beef with the rust compiler yesterday, every cargo check takes 20 seconds.
And then look at the three functions below, only one of them are Send, if you know why, please let me know.
(Note: value that is not Send cannot be held across an await point, and Box<dyn Error> is not Send)
async fn one() {
let res: Result<(), Box<dyn Error>> = do_stuff();
if let Err(err) = res {
let content = err.to_string();
let _ = do_stuff(content).await;
}
}
async fn two() {
let res: Result<(), Box<dyn Error>> = do_stuff();
let content = if let Err(err) = res {
Some(err.to_string())
} else {
None
};
drop(res);
if let Some(content) = content {
let _ = do_stuff(content).await;
}
}
async fn three() {
let content = {
let res: Result<(), Box<dyn Error>> = do_stuff();
if let Err(err) = res {
Some(err.to_string())
} else {
None
}
};
if let Some(content) = content {
let _ = do_stuff(content).await;
}
}
You are running into the Send Approximation being too conservative. The compiler does not like to see a let binding for a non-Send type and an
.awaitstatement in the same scope. It is not (yet) smart enough to know that the non-Send type is already consumed by the time of the.await.You’ve already discovered the workaround in your
three(). To make it more conciseasync fn four() { let content = do_stuff().err().map(|err| err.to_string()); if let Some(content) = content { let _ = do_stuff_2(content).await; } }Rust output is bad? I feel like it’s one of the best in terms of telling you where you got things wrong. Nix output when you accidentally get infinite recursion is so bad.
Come to think of it, Nix fits all three better than Rust.
Ah yes, the good old random pile of unclear errors because you forgot to add the file in git thanks nix
random pile of unclear errors
warning: Git tree ‘/path/to/repo’ is dirty
Unfortunately, that shows up even when you’ve just modified an existing file, which is not a problem for it.
And which also happens to be the state my repo is in basically all the time, because I’ll change some setting, then see if it works like I want it to before making a commit…
People who’ve never used Rust or only used it once and couldn’t grok it like to meme that Rust is bad to cope.
Yes, preferring a language that’s easy to read and therefore easy to maintain over a language like Rust is definitely coping 🙄
preferring Rust over Rust? what do you mean?
do you think loosely typed python is easy to read and maintain?
I’ll stick with Go TYVM
Yeah, like, who would ever want to
stuff1()?.map(stuff2);It’s much better to just:
err, value = stuff1(); if err == nil return err, nil; if value != nil stuff2(value);And you might even:
for a in vec { vec[a] }
cargo() { cargo $@ echo So how you doin\' today? }Fixed
Just a guess, but are you missing
+ Sendon your error type?So a narrow but clear win for the Rust compiler still…
I thought the rust compiler was supposed to be polite and helpful (unlike gcc, or nix).
It is, this meme is just trash.
gcc was unhelpful a couple decades ago. I’ve found it to be rather helpful in recent years.
Yeah, recent versions of GCC have gotten a lot better. I suspect it’s actually because of languages like Rust raising the bar.
No, Rust came later.
they didn’t say otherwise
They literally did. They theorized that Rust influenced GCC’s improved error messaging. That could not have happened if GCC improved their error messaging prior to the existence of Rust.
no they didn’t, yes it could have happened:
- GCC: exists, not too good messages
- rust gets made
- rust gets popular
- gcc error messages get improved by good example of rust
gcc is not a dead project. it is continuously maintained. its improvements can be influenced by other projects like rust
I love the rust compiler, it makes debugging so easy
https://xkcd.com/303/ vs this guy who thinks 20 seconds is a long time
“This could take like a hundred milliseconds. It could even take gasp ONE WHOLE SECOND! 😱”
