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[Feature request] User defined type guards like TypeScript's one #2476
Description
As a simple example, I would like to annotate the following @guard x string. This is in effect returning a boolean, which narrows down the type of the argument x.
---@param x unknown
---@guard x string
local function isString(x)
return type(x) == "string"
end
---@param x string | number
local function main(x)
if isString(x) then
-- x is string
print(x)
else
-- x is number
print(x)
end
end
Activity
firas-assaad commentedon Jan 12, 2024
I'd like this feature as well. It's been proposed a couple of times in the past, but it's apparently hard to implement: #1030 (comment)
itsDesignFlaw commentedon Jan 28, 2026
2 years later, is there any chance of getting this?
CppCXY commentedon Jan 28, 2026
emmyluals support this like: