On Fri, Mar 14, 2014 at 3:34 PM, John Barton <[email protected]> wrote:
> On Fri, Mar 14, 2014 at 11:42 AM, David Herman <[email protected]> wrote:
>> When you export from a module, you're exporting bindings, rather than
>> values. This means you can refactor between
>>
>> module m from "foo";
>> ...
>> m.bar
>>
>> and
>>
>> import { bar } from "foo";
>> ...
>> bar
>>
>> and they're fully equivalent.
>
> Ok great, so one solution to potential confusion caused by 'import' is
> simply to always use 'module'.
Another way to put this is that changing:
```js
import { bar } from "foo";
```
to
```js
module m from "foo";
let bar = m.bar;
```
will always be a subtle source of bugs.
Looked at another way, the module spec is introducing a new sort of
assignment statement, where the bindings are mutable. But instead of
adding this as a high-level feature of the language, it's being
treated as a weird special case for modules only.
I would be happier introducing a general purpose "mutable binding
assignment" like:
```js
let mutable bar = m.bar;
```
where every reference to bar is always treated as a dereference of
`m.bar`. That way the new assignment feature isn't pigeonholed as a
weird part of the module spec.
Couldn't we assemble the desired semantics out of pre-existing
primitives, instead of inventing new stuff? For example, if `m.bar`
in the example above was a proxy object we could preserve the desired
"mutable binding" without inventing new language features.
--scott
ps. I foresee a future where modules are (ab)used to create mutable
bindings. Better to make them first-class language features!
pps. Circular references work just fine in node. You have to be a
little careful about them, but the 'mutable bindings' don't change
that. They just introduce `bar` as a new shorthand for writing
`m.bar`. IMHO the latter is actually preferable, as it makes it
obvious to the author and reader of the code exactly what is going on.
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