What are the correct semantics of a closure over a loop variable? [closed]

Answer 1

The Lua manual explains exactly why this works. It describes the index for-loop in terms of a while loop as this:

 for v = e1, e2, e3 do block end

--Is equivalent to:

 do
   local var, limit, step = tonumber(e1), tonumber(e2), tonumber(e3)
   if not (var and limit and step) then error() end
   while (step > 0 and var <= limit) or (step <= 0 and var >= limit) do
     local v = var
     block
     var = var + step
   end
 end

Notice how the loop variable v is declared inside the scope of the while loop. This is done specifically to allow exactly what you're doing.