Narrowing Types Issue

还没有人认领这个 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 扩展中复现 Lua 代码片段，并跟踪最后两个分支的类型检查行为。当推断出的类型与报告一致时即完成：var8 为 false，var9 为 true，var10 为 false，同时前面的变量保留其列出的类型。

由索引模型根据 Issue 内容生成。