New Type Solver [Beta]

[robloxdestroyer1035]

Yeah, this one was really confusing. Why would it be trying to convert false to true? Not sure why an error would be raised here since TRUE and FALSE are both booleans

[NemusCraft (Nemusy)]

I didn’t even have memory issue, but autocomplete are broken for me.

[WheretIB]

@ForeverDev

Very exciting changes! However – I accepted the beta feature and my Studio memory shot to 50gb (yes, gb.) and then crashed. I turned the beta feature off, restarted, and now my standard type checking doesn’t work at all

@CoderJoey

This is a fantastic update to Luau!!! But unfortunately I tried enabling the setting for our game (Pet Simulator 99, and Pet RNG) and the solver freezes internally and starts allocating gigabytes of RAM until my computer completely runs out of memory.

The memory use should be more limited in the recent Studio update 644.
I would still suggest waiting for a few months more before enabling it on large projects with heavy use of strict typing as it can take a long time to complete, blocking auto-complete.

@4_mer

Studio just closes for me after loading up the game

Can you please check if this still happens when you open your place in Studio version 644?

[daz_fe (Drastic)]

this is a great update! however it always crashes when i open a place file

[malakopter (Malakai)]

This feature was causing my Roblox Studio to crash on start-up, it would seem. Though only when opening a specific place, our team uses a lot of Luau so I’m assuming some collision somewhere caused something to crash. I’m not even sure how that would work but something to look into. Thanks I’m excited for this change

[amets_iratxo (iratxo)]

We definitely ran into a few new crashes that we’ve been working hard on fixing with the beta release! We suspect the 646 release should contain the last of the fixes for the big batch of crashes we’ve seen so far. So, I’d recommend folks who had crashes to try again next week once 646 has been released for a bit (it takes time for us to get all the flags on and so forth), and let us know if they’re experiencing crashes still.

It’s possible you’re encountering one that is new and we haven’t seen yet, and we’ll definitely keep an eye out for new crashes and investigate them as best as we can. If you experience one and want to help out, opening a DevForum bug report that includes a description of the crash, explicitly notes that it was in the New Type Solver Beta, and includes (privately) the attached place file would be tremendously useful in helping us diagnose and resolve the crash expediently! Cheers!

[JaythemanCHS]

This beta seems to not work on my end sadly. Whenever opening any place, even the template baseplate, my memory usage continues to increase until it’s used all that’s available. I can still use Roblox Studio during this, but the IntelliSense and autocomplete fail to work.

[NGC4637 (NoMore_Sugarcoating)]

I’ve seen a few issues

1. math operations in different closures (most if not all)

--!strict
--!strict
local i: number = 0
task.defer(function()
	i = i + 1
	if i >= 3 then
		-- something
	end
end)

i + 1 and i >= 3 triggers warnings, however changing it to i += 1 solves both issues
if i remove the task.defer, it’s also fine.

So, typechecking for local variables in the same scope but seperate closure is very whack

2. typeof() on generics

--!strict
local function sine<T>(amp: T, len: T, off: T, step: number?): T
	if type(amp) ~= "number" and type(amp) ~= "vector" then error(`invalid argument #1 (number or vector expected, got {typeof(amp)})`) end
	if typeof(len) ~= typeof(amp) then error(`invalid argument #2 ({typeof(amp)} expected, got {typeof(len)})`) end
	if typeof(off) ~= typeof(amp) then error(`invalid argument #2 ({typeof(amp)} expected, got {typeof(off)})`) end
	
	local x = step or os.clock() * 60
	if type(amp) == "number" then
		return amp * math.sin(x/len + 0.015707963267948967*off)
	elseif typeof(amp) == "Vector3" then
		if amp == Vector3.zero then return amp end
		return amp * Vector3.new(
			math.sin(x/len.X + 0.015707963267948967*off.X),
			math.sin(x/len.Y + 0.015707963267948967*off.Y),
			math.sin(x/len.Z + 0.015707963267948967*off.Z)
		)
	end
	
	if amp == Vector2.zero then return amp end
	return amp * Vector2.new(
		math.sin(x/len.X + 0.015707963267948967*off.X),
		math.sin(x/len.Y + 0.015707963267948967*off.Y)
	)
end

this entire code is littered with warnings

• Type function instance union<*blocked-1234*, nil> is uninhabited on 3, 8, 10
• Operator '== or ~=' could not be applied to operands of types string and *blocked-1234*; there is no corresponding overload for __eq on 4, 5
• Type function instance intersect<T, number> depends on generic function parameters but does not appear in the function signature; this construct cannot be type-checked at this time on 9, 11-16, 19-23

3. odd thing with tables

--!strict
local a = table.create(1)
a[1] = {}
table.insert(a[1], "test")

line 3 gives the error Type '{ }' could not be converted to 'nil'
line 4 gives the error None of the overloads for function that accept 2 arguments are compatible.
type solver seems to assume a[1] is nil for some reason
i first saw this issue with modules generated by Blink IDL, Queue and Events table create a ton of warnings with this same issue i just mentioned

[Vanniris (Vanni)]

big block number!

this happened after casting a table with index:

local t = {} :: index<typeof(tbl), T> -- where T is a generic

and running t through a function that would otherwise return a table:

local copy = table.clone(t) -- *blocked-xxxxxx* Function only returns 0 values, but 1 is required here

[mariuslohoho]

Issue

Currently, if I try to create a type for a table without a specific key, the code completion does not show the indexes.

(doesn’t work either way with any or unknown)

• (this wouldn’t work too as Table2 has not been defined yet)

• Using string literal union doesn’t work

• Neither does using another type works

Suggestion

• Could we get a solution like in typescript and/or vscode, where there is Record<> and code completion even if the index is not specified?

[kalrnlo (witchiest)]

@mariuslohoho

• Using string literal union doesn’t work

Unions are done using | not ,

{ ["apple" | "banana"]: string }

also you could type it as a struct

{
    apple: string,
    banana: string
}

also btw the solver not giving suggestions for { [string]: string } is a bug and should work

[kalrnlo (witchiest)]

What your wanting is, is a type provided by roblox that takes in a string and gives the equivalent instance type ie

function get_children<C>(class: C): { Instance<C> }

ene

you can technically do this rn, but instance.new doesnt work with typeof

function get_children<C>(class: C): { typeof(Instance.new("" :: C)) }

end

Note: you also need to use generics for this

Type checking

[Vizzun]

One thing I have noticed is that the new type solver fails to recognise the types of function parameters when defining pre-typed functions.

For a bit of context: I’m using a unique type to override the RemoteFunction type, allowing me to get typechecking on remotes both on the server and client — without having to add types to the parameters more than once.

[crazyattaker1]

For some reason I no longer get autocompletion after enabling the “New Luau type solver” beta feature, is there anything I need to do to get it working again?

[mariuslohoho]

• The key is not showing up in the autocomplete

• But the value autocomplete still does

[Yesil_HiyarAlt (Crypt_Blade)]

Not sure if it is possible now but it’d be nice to be able to get an automcomplete in cases like this (very simplified, usually theres a bit more going on)

instead of having to specify it as a typeof({}) which i feel is a bit weird. (unless the table is specifically frozen, with table.freeze, i feel this should happen because its kind of untrue to whats actually going to happen)

[Mikos_Drafle (mikoblixel)]

i dont get any autocompletion anymore after enabling this beta. what gives? setting the “self” variable used to be so reliable, but now the self variable’s type is no longer recognized. neither do if statements work, checking for parts in the player character is worse now as every type is “unknown”

[M_nzter (MonzterDEV)]

@welblander

New Type Functions: keyof, rawkeyof

keyof has made using Luau so much more enjoyable omg

[gwenniekins]

Using the new Type solver has a strange issue, in the which it seems the first line of EVERY script that has any form of type checking(unless using typeof/type/:IsA()) has a warning, it doesn’t matter what’s there, it could just be whitespace, and it’d still have a warning on line 1

not done a huge amount of testing, but I’ve confirmed it’s because of the new type solver.
(also there’s a topic about it from someone else : Weird line on the first line of every script)

[crusherfire]

Is it now possible to create dynamic parameter types based on previous arguments?
Similar to something mentioned in this post:

Typechecking: How would you change an expected parameter type depending on the value of a previous argument

Hi, So I’m just wondering how I would go about changing a function’s expected parameter type depending on some other parameter? In my example I’m working with a folder of different values which relate to certain round stats (eg. round time, round status etc), all of which are different types of value bases. So, suppose you go about approaching it by creating a module to set these values instead of just setting it manually (works better with my workflow): local module = {} function module:Se…

I’ve tried seeing if I could make dynamic parameter types but I haven’t found a working solution yet.

EDIT:
Something like this sorta works? Although it won’t pick the type of the second argument. It’ll only list out all the possible arguments.

type Args = {
	Confetti: { Position: Vector3 },
	Explosion: { Radius: number }
}

type ExampleFunc<T = keyof<Args>> = (effect: T, args: index<Args, T>) -> ()