LuaLS / LuaLS/lua-language-server

Infer pcall arguments from the first function parameter

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Dominant language
Lua
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Description

Hi 👋

I was wondering if it would be possible for LuaLS to infer the types of the arguments passed to pcall based on the signature of its first function argument. This would significantly improve developer experience, especially when working with typed Lua (e.g., EmmyLua annotations) or when relying on auto-completion and type checking.

Example:
local function greet(name: string)
  print("Hello, " .. name)
end

pcall(greet, "world") 
             ^- here we should see `name: string`

In this case, it would be great if LuaLS could infer that greet expects a string, and therefore type-check or suggest "world" accordingly when passed to pcall.

Currently, the parameters after the first one are not checked or suggested with much context, making it less ergonomic when using pcall (or other similar functions) for safe calls.

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Research direction

Start by tracing how LuaLS handles the pcall call shown in the example and how it checks arguments against a function signature. Identify the relevant type-checking and completion paths, then verify that arguments after the first function parameter receive the expected context for typed Lua calls.

Written by the indexing model from the issue text.

Assessment

Tech stack
lua
Domain
developer-experience, devtools
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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