More diagnostics

[sumneko]

local t = {}
for i = 1, 10 do
    if xxx then
        goto continue
    end
    t[i] = true --> warning: sparse array
    ::continue::
end

[sumneko]

mark = true
marks[xxx] = true
if xxx then
    return
end
mark = nil --> warning: may be not reset
marks[xxx] = nil --> warning: may be not reset

[firas-assaad]

I don't use the pattern in the sparse array example, so I can't say much about it. Is it only for goto? What if you have something like this?

local t = {}
for i = 1, 10 do
    if xxx then
        t[i] = true
    end
end

Checking if the developer wanted to reset the variables to nil makes sense in theory. I did find a few examples in my code that set values to nil to mean "no value specified" instead of attempting to reset a variable, but it depends on how deeply the code will be analyzed.