table newindex shows invalid `need check for nil` warning if key is `false`

How are you using the lua-language-server?

NeoVim

Which OS are you using?

Windows

What is the issue affecting?

Type Checking

Expected Behaviour

t[key] = {} should throw no warning if key is not nil.

Actual Behaviour

t[key] = {} throws an invalid warning if key is false but not nil.

Reproduction steps

local CACHE = {}
CACHE[false] = {} -- ok
local key = false
CACHE[key] = {} -- should be ok as well, but throws invalid warning

Additional Notes

This happened to me in a more complex method where I ensured a key is not nil, by redefining the parameter:

function apicall(input)
    local key = input or false
    -- more stuff...
    cache[key] = {}
    return cache[key]
end

I'd like to note an annoyance when it comes to casting, the following casts all throw warnings, even if explicitly casting the variable, requiring me to invent a new variable (or forcing me disable redefining local):

---@param input string?
function apicall(input)
    -- this cast does nothing and also throws no warning
    ---@cast input +false
    -- this cast warns that it can't cast string? to string|false
    ---@cast input string|false

    -- this is what I do, it just throws an info warning, which I've disabled:
    ---@type string | false
    local input = input or false
end

Log File

No response

Commencez par la reproduction en Lua dans l’issue et suivez le chemin de vérification des types pour les opérations table newindex lorsque la clé vaut false plutôt que nil. Examinez également les exemples de cast signalés, puis vérifiez que les clés valides ayant la valeur false ne produisent plus l’avertissement, tandis que les clés réellement nil le produisent toujours.