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

首先，在 Windows 上的 Visual Studio Code 擴充功能中重現 Lua 程式碼片段，並追蹤最後兩個分支的型別檢查行為。當推斷出的型別與報告一致時即完成：var8 為 false、var9 為 true，且 var10 為 false，同時前面的變數保留其列出的型別。