`string.gmatch` and `string.match` have invalid return types

[sewbacca]

How are you using the lua-language-server?

NeoVim

Which OS are you using?

Windows

What is the issue affecting?

Annotations, Type Checking

Expected Behaviour

The return type of string.match should be string|integer? and the return type of string.gmatch, should be a function which returns multiple string|integer ...

Actual Behaviour

The return type of string.match is any and the return type of string.gmatch is (fun(): string, ...), which causes #2487

See

lua-language-server/meta/template/string.lua

Lines 90 to 96 in 0187ddf

	---#DES 'string.match'
	---@param s string|number
	---@param pattern string|number
	---@param init? integer
	---@return any ...
	---@nodiscard
	function string.match(s, pattern, init) end

and

lua-language-server/meta/template/string.lua

Lines 54 to 67 in 0187ddf

	---#DES 'string.gmatch'
	---#if VERSION <= 5.3 then
	---@param s string|number
	---@param pattern string|number
	---@return fun():string, ...
	---@nodiscard
	function string.gmatch(s, pattern) end
	---#else
	---@param s string|number
	---@param pattern string|number
	---@param init? integer
	---@return fun():string, ...
	function string.gmatch(s, pattern, init) end
	---#end

Reproduction steps

Try casting the first for loop variable from a :gmatch() into an integer (---@cast x integer), it throws an invalid warning; see no completion of return values from a :match().

Additional Notes

It seems to be currently not possible to specify types for ... return types using the fun() syntax. As a workaround at least define the first return value as string|integer instead of string.

Log File

No response

[carsakiller]

I was very confused by string|number until I remembered that there is the "index" syntax for patterns ()! Good catch!

local header = "i\ttype\tmatched text"
local txt = "name=steve,color=blue"

print("string.match")

local str = header
local t = { string.match(txt, "()(%w+)=([%w]+)()") }
for k, v in ipairs(t) do
	str = str .. string.format("\n%s\t%s\t%s", k, type(v), v)
end

print(str)

--

print("\nstring.gmatch")

local str = header
local f = string.gmatch(txt, "()(%w+)=()([%w.]+)")
local i = 0
while true do
    i = i + 1
	local t = { f() }
    if #t == 0 then break end

	for k, v in ipairs(t) do
		str = str .. string.format("\n%i-%s\t%s\t%s", i, k, type(v), v)
	end
end

print(str)

string.match

i	type	matched text
1	number	1
2	string	name
3	number	6
4	string	steve

string.gmatch

i	type	matched text
1-1	number	1
1-2	string	name
1-3	number	6
1-4	string	steve
2-1	number	12
2-2	string	color
2-3	number	18
2-4	string	blue

I'll take a look at this in a bit. If only we could append ... for variadic returns like fun(): string|integer... for gmatch.