Corner case Lua assignment bug

do local a = {}; a[1], a = 1, 2 end
do local a = {}; a[1], a = (function() a = nil end)(), 2 end
do a = {}; a[1] = (function() a = nil end)() end

-- uh oh. this one indexes nil
do local a = {}; a[1] = (function() a = nil end)() end -- error!
-- and of course there's nastier examples
do
    local a = {}
    local b = setmetatable({}, { __add = function() a = nil end })
    a[1] = b + 0 -- bang! fails as well
end