catching writes to loop index

[Asko Kauppi <asko.kauppi@...>]

Lua 5.0 refman says:

"The behavior [of the iterative for statement] is undefined if you 
assign to var_1 inside the block."

As we all know, this means that 'for k,v in pairs() ..blahblah..' you 
must not (never, ever!) change the 'k' within the loop. For other 
iterators (s.a. lines()) there may be only one var returned that should 
not be changed.  It's always the first.

The point is:

- Could the Lua interpreter detect the write within it's parsing, and 
simply refuse to compile such code.  I feel this would be very welcome, 
and smoothening to Lua newbies especially, since otherwise the program 
just works erroneously without an obvious reason.

What do you say?

-ak