upvalues actually are values?

[spir <denis.spir@...>]

Hello,

In most languages with function closures, the following piece of code would 
print 1 and 2:

inc = function (i)
   return function (n) return n+i end
end

i = 1
inc1 = inc(i)
print (inc1(0))

i = 2
print (inc1(0))		--> 1 or 2 ?

The reason is that so-called upvalues usually not are values, but "up-vars". In 
fact, what the closure closes on is the variable, here i, not its piece of data 
[1]. Anyway, this is very common [2], some even call this behaviour only "true" 
closures. (This may have fit well in Lisps of the dynamic scoping flavour.)

Seems like Lua does (what I consider) the right thing, here. How are closures 
really built and what is there theoretical semantics on this point? (I did not 
really find answers in docs).
Also, has anything changed in Lua recently about this question?

Thank you,
Denis

[1] No idea why one would want that, since it kind of implicitely breaks 
referential transparency (the func now really depends on an external var), and 
maybe even lexical scoping (depending on how you understand it).

[2] An exception is OCaml, not because upvalues are values, but because the 
second assignment would create a new *variable*, thus unrelated to the closure.