Hi David,
First of all, I think you may not be reading the current "private names"
proposal. Allen wanted to change the name so he created a new page:
http://wiki.ecmascript.org/doku.php?id=strawman:private_names
Part of what you're reacting against is in fact what he changed (more below).
But let me answer your question to provide some background.
> It feels to me as if the private declaration is behaving like a macro.
>
> Are there precedents for this kind of meta-identifier in other languages?
It might be illuminating to know that this whole line of exploration started
when I was reading the documentation for PLT Scheme (now called Racket), which
has a library for creating generative, lexically scoped names for use with
their object system. You can write:
(define-local-member-name foo)
and then use `foo' as a property in a class, and only the code in the scope of
the `define-local-member-name' can access that property name.
In other words, that's where I got the idea for the original private names
proposal. And yes, internally, the implementation defines `foo' as a macro that
expands into the gensym'ed name.
What also might be illuminating is the fact that this is part of the Scheme way
of doing things, which is never to have more than one lexical environment. So
absolutely everything in Scheme shares a single "namespace" --
`define-local-member-name' and macros and keywords and variables and anything
fancy new binding forms you can invent (via macros, of course!).
I probably followed this approach without even thinking explicitly about it,
because I'm so used to the Scheme Way. :) So my original proposal worked very
much the same as `define-local-member-name'.
But Allen convinced me that there are drawbacks to having the single namespace,
especially since '.' and ':' are a separate syntactic space from variable
references. He reworked the proposal so that `private' binds in a *separate*
namespace from variables, so there's no conflict between the two. Take a look
at his proposal and see what you think.
Dave
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