Can not infer basic assignments in nested loop.

Discussed in https://github.com/LuaLS/lua-language-server/discussions/2471

^{Originally posted by Luke100000 January 8, 2024}
Why can it not infer the type here? How would I rewrite this to be type conform, without spamming type annotations?

local y = 0

for i = 1, 2 do
    y = y + 1 -- here, y is inferred as an integer correctly

    for j = 1, 2 do
        y = y + 1 -- can not infer type
    end

    -- sometimes a bit more complexity is required to trigger the issue, so lets add another loop
    for j = 1, 2 do
        y = y + 1 -- can not infer type
    end
end

print(y)

首先复现 issue 中的嵌套循环示例，并阅读 discussion 2471 以了解现有分析。跟踪 language server 如何通过循环中的赋值推断 y。当所示赋值能够保留推断出的 integer 类型，而不需要重复的类型注解时，即视为完成。