LuaLS / LuaLS/lua-language-server
Missing diagnostic when calling a non-function value
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- Lua
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Description
### 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?
Diagnostics/Syntax Checking
### Expected Behaviour
LuaLS should report a diagnostic when a value whose type is known to be non-callable is called like a function.
For example, calling a `number`, `string`, `boolean`, or a plain table without a known `__call` / `@overload` signature should produce a warning/error, because the code will fail at runtime.
### Actual Behaviour
No diagnostic is reported.
Even when the value is explicitly annotated or cast as `number`, LuaLS accepts the call silently.
### Reproduction steps
Use the following code:
```lua
local x = 1 --[[@as number]]
x()
local y = 1
y()
---@type number
local z = 1
z()
```
Expected: diagnostics on x(), y(), and z().
Actual: no diagnostics are reported.
At runtime, these calls fail with an error similar to:
attempt to call a number value
### Additional Notes
This is different from callable table / __call support.
I am not asking LuaLS to reject values that are explicitly annotated as callable, for example with ---@overload fun(...) or an equivalent __call signature.
The issue is about direct calls to values whose inferred or declared type is definitely not callable, such as number.
This also affects typo detection. For example, code like this can accidentally parse as a function call:
```lua
---@param name string
local function greet(name)
return "Hello " .. name "!"
end
```
Here name "!" is a call expression, but name is a string, so a diagnostic would be useful.
### Log File
_No response_
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the issue with the Lua snippets calling number and string values, then trace the diagnostics or type-checking entry point that handles call expressions. Done means diagnostics are reported for definitely non-callable values while callable tables and values with explicit overload or __call signatures remain accepted.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- lua
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 65/100