LuaLS / LuaLS/lua-language-server
[Feature request] User defined type guards like TypeScript's one
Open
Nobody has claimed this yet.
enhancement
feat/LuaCats Annotations
feat/type check
- Dominant language
- Lua
- Stars
- 4.4k
- Forks
- 442
- PR merge metrics
- No merged PRs in 30d
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
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
The issue names no files, tests, or entry points. Start by comparing the requested @guard annotation and isString example with the language server's existing type-narrowing behavior. Done means user-defined guards narrow x to string in the true branch and to number in the false branch.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- lua
- Domain
- devtools
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 30/100