Error: Request textDocument/signatureHelp failed.

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?

Completion

Expected Behaviour

VSCode shows function arguments normally.

Actual Behaviour

"Request textDocument/signatureHelp failed" is shown.

[Error - 4:54:31 PM] Request textDocument/signatureHelp failed.
  Message: [16:54:31.780][error][#0:script\core\signature.lua:56]: script\core\signature.lua:56: attempt to index a nil value (local 'argLabel')
stack traceback:
	script\core\signature.lua:56: in upvalue 'makeOneSignature'
	script\core\signature.lua:175: in upvalue 'makeSignatures'
	script\core\signature.lua:209: in function 'core.signature'
	script\provider\provider.lua:783: in function <script\provider\provider.lua:770>
	[C]: in function 'xpcall'
	script\proto\proto.lua:202: in function <script\proto\proto.lua:177>

  Code: -32603 

Reproduction steps

Test code:

---@class ColorClass
local Color = {}

---@alias Color ColorClass|number[]
---@alias AlignMode
---| "center"
---| "left"
---| "right"
---| "justify"

---@param args string|{text:string,wrap:boolean?,font:{path:string,size:integer}?,scale:number?,align:AlignMode?,color:Color?,outline:number?,outlineColor:Color?}
local function fooz(args)
end

The args has to be quite long to trigger it and perhaps with that specific setup of Color and AlignMode too.

Afterwards, simply write fooz( on the next line and the error should appear.

Additional Notes

No response

Log File

file_d%3A_Data_Development_love-11.3-win64_luals-report.log

fooz( と入力してシグネチャ ヘルプを要求し、Lua スニペットで失敗を再現します。script/core/signature.lua:56 から開始し、次に traceback に表示される makeSignatures とプロバイダーの呼び出しフレームをたどります。リクエストでエラーが発生しなくなり、VS Code がこの宣言の関数引数を表示すれば完了です。