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

まず、提供された ?? の例を使って lua-language-server の型チェッカーで問題を再現し、次に推論された型を同等の or 式の型と比較します。nil-coalescing 式が nullable オペランドをどのように処理するかを追跡します。bar が integer と推論され、比較ケースに対する既存の動作が正しいままであれば完了です。