What does this "@" mean

Deadx_scripts · June 28, 2024, 4:56am

Hi everyone,
I hope you’re all doing well! I was casually scripting when I encountered an unfamiliar “@” that I couldn’t find any information about.
Screenshot 2024-06-28 145037
Despite my efforts to research it, I haven’t been able to discover what this “@” means. Could someone provide me with some insight?

K4ttt_i · June 28, 2024, 4:59am

github.com

luau-lang/rfcs/blob/master/docs/syntax-attributes-functions.md

# Attributes (for Functions)

## Summary

Add a syntax for attributes to function declarations in the style of `@name` that can be placed before their declarations to adjust the behavior of the compiler, analyzer, and runtime.

These attributes would be valid in both the normal syntax for declaring functions and the syntax for anonymous functions, with or without locally scoped names.

Due to attributes being tied to the language's behavior, this proposal does not allow for them to be implemented by users. A mechanism to do so would be either very complex or wildly unsafe and is thus not considered by this proposal.

## Motivation

It's desirable to have control over various parts of Luau. Consider three potential attributes:

- `@native`, to indicate that a function should be compiled using native codegen
- `@inline`, to indicate that a function should be inlined where called
- `@deprecated`, to indicate that a function should be marked as deprecated by the analyzer

Right now, `@native` has an equivalent directive at the top of scripts in the form of `--!native`, albeit for the entire chunk being processed. In the future however, this may be guided by heuristics on a per-function basis to determine if doing so is 'profitable'. While cost models of this nature can be extremely well tuned, they tend to err on the side of caution so are not always correct. Without some way to indicate that a specific function should be natively compiled, users are at the whim of a cost model that might change unexpectedly and negatively impact performance.

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Deadx_scripts · June 28, 2024, 5:15am

I am still struggling to understand:
Screenshot 2024-06-28 151342

Both “@native” and “@example” come back as a error.
Is there something that I misread or missed?

mustedcloud · June 28, 2024, 5:24am

interesting i wounder what it could be

K4ttt_i · June 28, 2024, 5:29am

Basically they can only be used in a very unsafe and difficulty way so it’s recommended to not use them. And the attributes in the documentation are given as an example, you have to declare them first.

mustedcloud · June 28, 2024, 5:32am

so they are useless and even if I were to use them they would break studio

K4ttt_i · June 28, 2024, 5:36am

Sort of…? That’s the only documentation I could find about them… I myself just saw about them in the new release notes topic.

K4ttt_i · June 28, 2024, 5:36am

Deadx_scripts · June 28, 2024, 5:36am

How would you declare an attribute?

mustedcloud · June 28, 2024, 5:40am

i think roblox is just playing around with it as a possible update in the future

Deadx_scripts · June 28, 2024, 5:41am

oh ok. so “@” is like another one of those scripting tricks like --!native and !strict.

K4ttt_i · June 28, 2024, 5:43am

Could be.

Yes, exactly. As the documentation states it’s just used to declare attributes for certain modules that affects their behaviour in runtime (running the game). And about your previous post which you deleted, they seem to be only be declared by roblox themselves, we cannot.

Deadx_scripts · June 28, 2024, 5:45am

Ahh, I got you now. Thank you for helping me understand.

K4ttt_i · June 28, 2024, 5:45am

No problem! Glad I could help! Now I also know what these things actually are lol.