Luau tagged result unions

Luau tagged result unions

Run as a standalone current Luau script, or as a Script in Roblox Studio ServerScriptService. No Roblox engine APIs are required; type-annotated syntax is not standard Lua.

--!strict
type Result = {ok: true, value: number} | {ok: false, message: string}
local function parse(text: string): Result
    local n = tonumber(text)
    if n == nil then return {ok = false, message = "invalid"} end
    return {ok = true, value = n}
end
local result = parse("21")
if result.ok then
    print(result.value * 2)
else
    print(result.message)
end

1. Output: 42. Passing non-numeric text prints invalid through the error branch.