Re: Idea for 5.2 : merging _ENV and ... (was: Re: reinstating "in env do ... end")

[Roberto Ierusalimschy <roberto@...>]

> I think it's not pretty because what I want to say is: "redirect
> global symbol lookup to this table", and not: "assign this table to
> a variable". I realise, of course, that _by_ assigning this table to
> _ENV, I get the lookup redirection, but that's implicit. This one
> symbol in the language is overloaded. It's magic.
> 
> [...]
> 
> See that's part of my issue with _ENV = { ... }. It's a reuse of
> existing syntax, but as a special case. However, nothing is perfect
> and the consensus seems to be that we can live with this one bit of
> magic in an otherwise perfect language ;)

I am not sure you have a correct understanding of how _ENV works. Any
reference to a "global" name 'x' ("global" here meaning a name
without any local declaration) is always translated to _ENV. That
is, if you write "x = x + 1", Lua reads this as "_ENV.x = _ENV.x +
1". That is all. Apart from this translation, _ENV is a completely
normal variable. An assignment to _ENV is a completely normal
assignment. There is nothing magic or special at all happening there.
_ENV is represented, stored, and manipulated by Lua just like any other
variable. Nowhere in Lua there is code like "if this variable is _ENV
then bla-bla-bla" (except for error messages).

-- Roberto