Using LuaJIT's nil-coalescing extension does not narrow the type correctly

How are you using the lua-language-server?

Other

Which OS are you using?

Linux

What is the issue affecting?

Type Checking

Expected Behaviour

Using the nil-coalescing operator should narrow an expressions type. For example, in this sample code, the type of b should be narrowed to integer:

---@type integer?
local foo = 1
local bar = foo ?? 2

Actual Behaviour

Instead of the type being narrowed, the type of foo is copied instead, and the type of bar is thought to be integer? instead of integer.

Reproduction steps

1. Insert the following sample code in a project:

---@type integer?
local foo = 1
local bar = foo ?? 2

2. Check the type of b

Additional Notes

This seems to work fine using the classic Lua approach with or:

---@type integer?
local foo = 1
local bar = foo or 2

The type of bar is integer here, as expected.

Log File

No response

首先，使用提供的 ?? 示例在 lua-language-server 类型检查器中复现该问题，然后将其推断出的类型与等价 or 表达式的类型进行比较。跟踪 nil-coalescing 表达式如何处理 nullable 操作数；当 bar 被推断为 integer 且现有行为对于比较情况仍然正确时，即表示完成。