Getting the Luau optimize level at runtime safely

LuauOptimizeLevel.lua

local function getOptimizeLevel()
    local function dupclosure()
      return function() end
    end

    local O0 = dupclosure() ~= dupclosure() 

    local function inlinefunction()
      return debug.info(1, "f")
    end
    
    local f = debug.info(1, "f")

    local O2 = f == inlinefunction()

    return if O0 then "O0" else (O2 and "O2" or "O1") 
end;

print(getOptimizeLevel())

Alternative that does not use debug.

local i = 0
local function it()
    if i == 0 then
    i = i + 1 
    pcall(it)
    else 
    i = i + 1 
    it()
    end
end
local function depth()
    it()
end
depth()

local function getOptimizeLevel()
    if i == 19998 then
    return "O2"
    end

    local function foo() return function() end end
    
    if foo() == foo() then
    return "O1"
    end

    return "O0"
end;

print(getOptimizeLevel())