False-positive type error: `vim.cmd` callable table flagged as "table cannot match fun(...)"

How are you using the lua-language-server?

NeoVim

Which OS are you using?

Linux

What is the issue affecting?

Diagnostics/Syntax Checking

Expected Behaviour

lua-language-server should recognize callable tables (with a __call metamethod) as valid function values. Passing Neovim’s vim.cmd to pcall should not raise a type error.

Actual Behaviour

lua-language-server reports a false-positive type error when vim.cmd (a callable table in Neovim) is passed to pcall:

Cannot assign table to parameter fun(...):...unknown
Type table cannot match fun(...):...unknown

Reproduction steps

1. In Neovim, open a Lua buffer (e.g., :new | set ft=lua).

2. Insert the following code:

   -- Works at runtime, but LuaLS flags the next line:
   pcall(vim.cmd, "redrawtabline")
   -- Diagnostic shown by LuaLS:
   -- Cannot assign `table` to parameter `fun(...):...unknown`
   

3. Observe the diagnostic from lua-language-server.

4. Execute the code in Neovim (e.g., :luafile %) to confirm it runs without runtime errors.

Additional Notes

• vim.cmd is a callable table provided by Neovim (implemented via __call metamethod). Direct calls like vim.cmd("redrawtabline") work at runtime. The false-positive only appears when passing vim.cmd as a function value (e.g., to pcall).

• Workarounds:

  -- Wrap in a function
  pcall(function() vim.cmd("redrawtabline") end)
  
  -- or use the typed API
  pcall(vim.api.nvim_cmd, { cmd = "redrawtabline" }, {})
  

• Please treat callable tables as functions for the purpose of type checking / inference.

Commencez par reproduire le diagnostic avec pcall(vim.cmd, "redrawtabline") dans un tampon Lua de Neovim, puis suivez les diagnostics de LuaLS et l’inférence de types pour les tables appelables dotées de métaméthodes __call. Le travail est considéré comme terminé lorsque les tables appelables sont acceptées là où des valeurs de fonction sont attendues sans masquer les véritables erreurs de type, et que la reproduction indiquée ne produit plus de diagnostic.