DIP16: Transparently substitute module with package

[Michel Fortin]

On 2012-04-04 19:48:32 +0000, "Steven Schveighoffer" 
<schveiguy at yahoo.com> said:

> On Wed, 04 Apr 2012 14:03:07 -0400, Timon Gehr <timon.gehr at gmx.ch> wrote:
> 
>> No symbol is resolved until semantic, but I don't think hiding the  
>> module/package symbol if any clashing symbol in the module/any  
>> subpackage exists is a satisfactory solution.
> 
> Then we must come up with a way to hide the submodules of a virtual module.
> 
> I tried this, which fails on the current compiler:
> 
> import x;
> 
> int x;
> 
> So it seems we have two choices here:
> 
> 1. DIP16 needs to get more complex to make package submodules not  
> accesible as individual modules.
> 2. Start contextually interpreting identifiers at least in the case of  
> modules vs. non-modules.
> 
> I'd suggest option 2 allows for better backwards compatibility and more 
>  flexibility.

I don't think option 2 is realistic (see my other post).

I don't think option 1 is an improvement over what we have. I mean, if 
you're going to hide the submodules, what is the benefit compared to 
just using a different package name for the implementation modules? You 
can already refactor std.algorithm this way with no change in the 
compiler:

	module std.algorithm;

	public import std.algorithm_impl.sort;
	public import std.algorithm_impl.map;
	public import std.algorithm_impl.blah_blah_blah;
	…

If we add a language feature, it should be an noticeable improvement 
over this situation.

I think we need a third option.

Here's an idea: we could allow modules having a single symbol with the 
same name as the module to behave as if they were the symbol itself, 
just like templates behaves. For instance:

	module std.algorithm.sort;

	void sort(int[] t);

Now you can import std.algorithm.sort and then use the 
std.algorithm.sort fully qualified name as if it was a function, even 
though it's the module name (std.algorithm.sort.sort would be the 
function's name).

Or maybe we could just allow "alias sort this" at module level? Or is 
it allowed already?


-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/