On 12/13/2013 02:57 PM, Piotr Kukiełka wrote:
I understand that one could want flexibility and matching file with
package is not always optimal.
And it's not what I wanted to suggest in first place ;)
Let's clear one confusion first. When I said that I think *mod* and
*extern mod* are redundant I thought about using them in context of
importing.
I do not think it is correct to think of `mod foo;` as importing
anything. Rust's module system is not based upon files: files are just a
convenience. "mod foo;" is literally just a shortcut for `mod foo {
<paste the contents of foo.rs or foo/mod.rs> here> }`. You could write
every crate in Rust as a single file per crate without changing the
semantics at all.
> Now, I don't see big difference between mod and extern mod, because
in both cases intention is very similar: you want to signalize that
required modules are in external crate.
`mod foo;` does not signify that modules are in an external crate, it
signifies that they are in the same crate. There are some big
differences to whether a module is in a separate crate or not. For
example, if crate Crate1 has a trait T and a type A, Crate2 cannot
implement trait T for type A. If T and A were in a different module of
Crate2, then it would be able to implement T for A. This is a very
important property of the crate system, and making it confusing by
merging `mod` and `extern mod` is a bad idea, in my opinion.
> This means to make it work correctly I need to add extern mod clib;
in both files (then it compiles and works).
No, that's not the case. To make it work you can do:
~~~
//------------------------- a.rs ---------------------------
mod b;
pub mod a_inner {
pub fn a_func() { ::b::clib::c_func2(); }
}
fn main() {
a_inner::a_func();
}
~~~
A similar modification will work with moving `extern mod clib` into a.rs.
The 'notices' you've written suggest to me that you don't completely
understand how the module system works today, which is very important to
do before suggesting changes to it (even if it's flawed you still need
to understand it). I suggest reading the relevant portion of the
tutorial again. All 4 'notices' you mentioned maybe become more clear then.
-SL
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