Narrowing Types Issue

How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

Which OS are you using?

Windows

What is the issue affecting?

Type Checking

Expected Behaviour

---@param param1 true | nil
---@param param2 false | nil
local function test(param1, param2)
	if param1 == nil and param2 == nil then
		local var3 = param1
		local var4 = param2
	elseif param1 ~= nil and param2 == nil then
		local var5 = param1
		local var6 = param2
	elseif param1 == nil and param2 ~= nil then
		local var7 = param1
		local var8 = param2
	else
		local var9 = param1
		local var10 = param2
	end
end

In this function the vars should have the following types:
var3: nil
var4: nil
var5: true
var6: nil
var7: nil
var8: false
var9: true
var10: false

Actual Behaviour

The actual values are:
var3: nil (correct)
var4: nil (correct)
var5: true (correct)
var6: nil (correct)
var7: nil (correct)
var8: unknown (incorrect)
var9: true | nil (incorrect)
var10: false | nil (incorrect)

Reproduction steps

1. Copy Code
2. See Issue

Additional Notes

No response

Log File

No response

まず、Windows 上の Visual Studio Code 拡張機能で Lua スニペットを再現し、最後の 2 つの分岐に対する型チェックの動作を追跡します。推論された型がレポートと一致し、var8 が false、var9 が true、var10 が false となり、それ以前の変数が記載された型を維持していれば完了です。