Comment by LatticeAnimal
9 hours ago
Is it obvious to rust developers that "!" would be the never type? I frequently use "never" in typescript. I could imagine using the never type frequently in rust too. I feel like a longer more human-understandable name would've been a good decision here. (feels like more rust jargon that makes the language harder to learn)
Even though the never type has been experimental for a while, I've seen `!` used in the docs,[0] so at this point, Rust developers are probably already aware of what it means even if they haven't used it before.
[0]: Example: std::process::exit returns `!` https://doc.rust-lang.org/1.0.0/std/process/fn.exit.html
You can even define your own functions that return `!` on stable Rust! The type has been stable in the return-type position since 1.0.
(There is a trick you can abuse to access the type everywhere: https://docs.rs/never-say-never/latest/never_say_never/)
Yeah I think just calling it 'Never' is much clearer, this isn't something that needs a dedicated single character, and ! is less readable imo
Agree. This is also what Swift uses.
Yeah it really baffles me why a symbol like `!` was spent on this, which could be more useful for more a more commonly used feature.
I just checked, my main side project only has less than 10 things that return never. `-> Never` reads even better, imo.
The exclamation point is also used both as the C-style negation operator and as the identifier suffix that indicates macro invocations, so it was unlikely that it would have been used for any new feature. As my sibling comment notes, this syntax for divergence is very, very old (predating even 0.1), not something that anyone newly came up with.
And if you'd like to write `-> Never`, the nice thing about being a first-class type is that you can now just do that if you'd like, via a standard type alias: `type Never = !;`.
> Is it obvious to rust developers that "!" would be the never type?
Prior to this change most Rust developers would never have cause to ever use `!` for any reason. The only stable way to do so would be to specify the quote-unquote "return type" of divergent functions, which Rust has supported via this special-cased syntax since prehistoric days, before even Mozilla got involved. You can see it in the oldest capture of the tutorial from Jan 2012: https://web.archive.org/web/20120109041112/http://www.rust-l...
So when it came time to elevate `!` from being a special-cased return type to being a fully-fledged type, it was only natural to reuse this syntax. However, I tend to agree that, because we call it "the never type" in casual conversation, the most natural thing to do would be to just have a type alias called `Never` that we could encourage people to use instead. But that would be a perfectly backwards-compatible change that could be made at any point (as proven by the fact that the stopgap and long-stable `Infallible` type is becoming just such a type).
> Prior to this change most Rust developers would never have cause to ever use `!` for any reason.
As a type.
"!" is in the most basic example nearly every rust developer has seen:
Unless you specifically watched a presentation or read a blog post about the never type, you probably haven't seen it as a type.
If the average (and nearly all new) rust developers encounters "fn bla(blub: i64) -> !" I suspect they will mostly go "huh??" (or wonder what kind of weird macro that is) until it becomes common to encounter early and gets it's own early entry in the rust book.
Compared to reading "fn blub(bla: &str) -> Never", which seems rather straight forward imo. However, "Never" might be the name of some actual Struct or Enum in various codebases.