• tcak (31/31) Oct 23 2014 The main function has following:
• anonymous (11/16) Oct 23 2014 Apparently std.stdio defines an alias `sock` to some module. When
• "Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> (11/24) Oct 23 2014 It's been discussed recently, but I can't find it now. It's a

"tcak" <tcak gmail.com> writes:

The main function has following:

- main.d -

	import test;
	auto t = new shared test.Test();
	auto sock = new std.socket.TcpSocket( 
std.socket.AddressFamily.INET6 );
	t.setIt( sock );


- test.d -

module test;

import std.socket;

public class Test{
	private std.socket.Socket s;

	public void setIt(S)( S sock) shared
		if(
			is(S: std.socket.Socket) ||
			is(S: shared(std.socket.Socket))
		)
	{
		s = cast( typeof( s ) )sock;
	}
}


Above code works properly (I mean there is no error at all).

=====

Then I change the "Test.setIt" method as follows:

		import std.stdio;
		s = cast( typeof( s ) )sock;


Error on "s = cast..." line:
cannot cast module socket of type void to shared(Socket)

===

What is casting a module? How is this happening? Is this a bird, 
superman, or a bug?

"anonymous" <anonymous example.com> writes:

On Thursday, 23 October 2014 at 18:43:54 UTC, tcak wrote:
 Then I change the "Test.setIt" method as follows:

 		import std.stdio;
 		s = cast( typeof( s ) )sock;


 Error on "s = cast..." line:
 cannot cast module socket of type void to shared(Socket)

Apparently std.stdio defines an alias `sock` to some module. When
you import std.stdio, its `sock` takes precedence over the
parameter `sock`.

I don't know if symbols from local imports should override
parameters just like that. There may be some room for improvement
here.

In the meantime, you can make the import static/renamed/selective:

static import std.stdio; /* must write `std.stdio.foo` */
import io = std.stdio; /* must write `io.foo` */
import std.stdio: foo; /* only foo is imported */

"Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> writes:

On Thursday, 23 October 2014 at 19:20:54 UTC, anonymous wrote:
 On Thursday, 23 October 2014 at 18:43:54 UTC, tcak wrote:
 Then I change the "Test.setIt" method as follows:

 		import std.stdio;
 		s = cast( typeof( s ) )sock;


 Error on "s = cast..." line:
 cannot cast module socket of type void to shared(Socket)

 Apparently std.stdio defines an alias `sock` to some module. 
 When
 you import std.stdio, its `sock` takes precedence over the
 parameter `sock`.

It's been discussed recently, but I can't find it now. It's a 
natural result of the scope hierarchy: parameters are in a higher 
scope than the function body, into which the identifiers from 
std.stdio get imported.

It's been recognized that this is often unexpected, and different 
lookup rules have been debated, but I think there was no clear 
conclusion.

But in this particular case, it has already been fixed, and will 
work in the next release:
https://github.com/D-Programming-Language/phobos/pull/2395