Luau generic parameters, specifically variadic namespace scope is 'global'?

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#1

I have multiple functions in my code which have typed variadic arguments.

Example:

function module.addCallback<P3...>(self: schema, fn: (P3...) -> (), ...: P3...)
	assert(type(fn) == "function")
	table.insert(self._callbacks, {
		fn = fn,
		args = table.pack(...),
	})
end

I had to name them ‘P3’ instead of just ‘P’ because in my object I use P for other functions. It appears that when this gets compiled into one big type, the P variable is getting shared with other types. I am not certain how this is playing out, but I will include the source code. It seems like one named type is poisoning the rest of them within a super-type.

--!strict

local module = {}

export type schema_raw = {}
export type schema = typeof(setmetatable({}, { __index = module })) & schema_raw

function module.new(): schema
	local self: schema = setmetatable({}::any, {__index = module})
	return self
end

function module.exec<P..., R...>(
	self: schema,
	fn: (schema, P...) -> ((number | string | boolean)?, R...),
	...: P...
): (number | string, R...)
	local reason = 0
	local results = { true, true }
	return reason, table.unpack(results::{any}, 3)
end


function module.ParseResult<R...>(
	reason: number | string,
	...: any --- This really should be R... but it does not work at all
): (boolean, string?, R...)
	if type(reason) == "number" then
		return false, tostring(reason), ...
	elseif type(reason) == "string" then
		return false, reason, ...
	else
		error("Impossible")
	end
end

function module.Simple<P..., R...>(
	fn: (schema, P...) -> ((number | string | boolean)?, R...),
	...: P...
): (boolean, string?, R...)
	local tx = module.new()
	return module.ParseResult(tx:exec(fn, ...))
end

image

If you change the second/third uses of P/R to something like P2/R2, it fixes the error. Additionally, I am unnable to change the “…: any — This really should be R… but it does not work at all” because it also results in an error:

image

Expected behavior

Types should not interfere with each other in different function declarations.

#2

Thanks for the report! Someone from our team will look into this.

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