How do Luau's compiler "--!" flags/comments work?

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#1

So, throughout time I’ve witnessed the usage of certain comments in Luau but I cannot find any documentation about it.

So, we got our well-known comments such as…

--!strict

--!non-strict

Which configure how strict the type-checking is.

There’s the native comments…

--!native

Which is used to mark an entire module script for Native Luau compilation and alternatively you can place @native above an function statement to manually mark a single function for native compilation.

Example:

@native
function NativeLerp(a, b, c)
  return a + (b - a) * c
end

(Theoretically this function should now be nearly as fast as if it were written in C++.)

Now about all the undocumented / lesser-known flags.

I’ve only seen this flag a few times
but placing --!optimize [Number] (I could have typed it wrong) at the beginning of a script forces a certain optimization level for a script?

The default for studio is level 1 and for live games it’s level 2 unless I’m missing something.
This is all I found really.

Where can I find more about flags like these? What’s the highest possible level? Can I use things like this in live games?

I wish to make use of Luau’s full potential and explore all the available comments/flags that can be placed at the start of a script but I don’t even know where to look.
Even Luau’s official site barely mentions any of these things existing at all unless my eyes skipped over something.

I wish there was more info and documentation on this, any help is greatly appreciated!

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#2
#3

I’ve looked through a bunch of threads but it seems like there is still very little information known.
So strange that so little is documented.

I’m still wondering if there are other flags besides --optimize 2.
I don’t doubt if there are but little to no results show up when looking for it.

#4

Here’s the full list of flags (or “hot comments”) the Linter recognises:

i.e. If you enter a comment such as --!fixmycode, it’ll check if it’s in the list, and since it isn’t, it’ll give you a linting warning and an orange underline.

Doing some analysis of the code above this section, we can also see the valid arguments for some of them:

  • nolint may optionally receive the Lint name to disable, taken from this list:
  • optimize expects 0, 1 or 2. Here is the explanation, in the code, of the effects of each of them:
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