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Description
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, Completion
Expected Behaviour
I am not sure this is a duplicate issue considering how common it probably is, but just to make sure.
Possibly a duplicate of #1583.
This is similar to #1146, but with returns instead of params.
It is a common pattern in Lua that on errors you might instead return a nil
value to imply failure, along side an error message.
---@return table
---@overload fun(): nil, string
local function fetchX() end
local resource, fail = fetchX()
if not resource then
print(fail:sub(1, 3)) -- fail type here is expected to be "string"
end
Actual Behaviour
You get a warning on fail
that it might possibly be nil. Because its type is string|nil
.
---@return table
---@overload fun(): nil, string
local function fetchX() end
local resource, fail = fetchX()
if not resource then
print(fail:sub(1, 3) )-- fail type here is actually "string|nil"
end
Reproduction steps
- Copy the setup code
- follow along with the comments
Additional Notes
I believe narrowing down the types in this case is still possible? It seems to me like #1583 was discussing the possibility of adding tuples, but shouldn't this be doable even without tuples support?
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