Unknown Vararg indices when itterated

[PennyJim]

How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

Which OS are you using?

Linux

What is the issue affecting?

Type Checking

Expected Behaviour

This is similar to #1355

When I try and itterate over a Vararg table, it'll be unable to determine the indexing value.

Actual Behaviour

My enabling of no-unknowns comes and bites me as the key is unknown.

Reproduction steps

---@param ... AnyType
function any(...)
  for key, value in pairs{...} do
    -- key is typed as an unknown instead of integer
    -- value is typed as AnyType
  end
end

Additional Notes

I've been told that there might be edge cases that are why this isn't how it currently works, but I thought I'd ask to at least find them out and learn more.

And if you are questioning why I'm using pairs instead of ipairs, that's because I'm modding in factorio with a deterministic pairs. It is actually faster than ipairs with functionally the same result, but with support for sparse arrays (this makes other Lua environments so sad to work with...).

Finally, I'm writing this at work in the morning before I forget, so I'm not being as thorough as I would prefer. I can absolutely get more information if requested.

Log File

No response

[tomlau10]

After some testing and reading the codebase, I think I have found the root cause:

• a table with purely varargs { ... } currently won't infer integer as one of the types of its key.

Analysis

The related logic is here:

lua-language-server/script/vm/sign.lua

Lines 114 to 117 in b815469

	if firstField.type == 'doc.generic.name' and firstValue.type == 'doc.generic.name' then
	-- { [number]: number} -> { [K]: V }
	local tfieldNode = vm.getTableKey(uri, node, 'any', true)
	local tvalueNode = vm.getTableValue(uri, node, 'any', true)

• in the reproduction code snippet, while the logic here can return AnyType for tvalueNode, it's returning nil for tfieldNode
• and then I looked into vm.getTableKey:

  lua-language-server/script/vm/type.lua

  Lines 711 to 725 in b815469

  	if tn.type == 'table' then
  	if vm.isUnknown(tnode) then
  	goto CONTINUE
  	end
  	for _, field in ipairs(tn) do
  	if field.type == 'tableindex' then
  	if field.index then
  	result:merge(vm.compileNode(field.index))
  	end
  	end
  	if field.type == 'tablefield' then
  	result:merge(vm.declareGlobal('type', 'string'))
  	end
  	if field.type == 'tableexp' then
  	result:merge(vm.declareGlobal('type', 'integer'))

• for a table type, currently only if it has tableexp, i.e. t = { 1, 2, 3 }, then it would consider integer type for its key

Solution

I changed line 724 to include varargs type

if field.type == 'tableexp' or field.type == 'varargs' then

=> then it works 🎉

maybe you can try open a PR on this after more testing 😄 @PennyJim