Hi,

I'm trying to use std.typecons.RefCounted on recursive structures to emulate garbage-collected classes, but it doesn't work, because the RefCounted implementation ends up creating a cycle in the structure hierarchy.

import std.typecons: RefCounted;

struct S
{
    RefCounted!S s; // error: struct S no size yet for forward reference
}

Even worst when I try to mix this with templates:

alias Node(T) = RefCounted!(_Node!T);
struct _Node(T)
{
    Node!T parent; // error: recursive template expansion
}

Is there some way to bypass these limitations, and use refcounted structures like classes?

Thank you in advance.

Am 10.05.2016 um 21:43 schrieb Lodovico Giaretta:
> import std.typecons: RefCounted;
>
> struct S
> {
>      RefCounted!S s; // error: struct S no size yet for forward reference
> }

This used to work with 2.067. I've filed a phobos regression for this very code, and two related dmd issues with different reductions:

https://issues.dlang.org/show_bug.cgi?id=16011 - [REG2.068] recursive RefCounted used to work
https://issues.dlang.org/show_bug.cgi?id=16012 - [REG2.070] forward reference with alias this
https://issues.dlang.org/show_bug.cgi?id=16013 - [REG2.072a] ICE with mutually dependent structs and alias this

Am 10.05.2016 um 21:43 schrieb Lodovico Giaretta:
> alias Node(T) = RefCounted!(_Node!T);
> struct _Node(T)
> {
>      Node!T parent; // error: recursive template expansion
> }

I think this is expected. Can't have cycles like that in template instantiations.

On Tuesday, 10 May 2016 at 22:10:06 UTC, ag0aep6g wrote:
> Am 10.05.2016 um 21:43 schrieb Lodovico Giaretta:
>> import std.typecons: RefCounted;
>>
>> struct S
>> {
>>      RefCounted!S s; // error: struct S no size yet for forward reference
>> }
>
> This used to work with 2.067. I've filed a phobos regression for this very code, and two related dmd issues with different reductions:
>
> https://issues.dlang.org/show_bug.cgi?id=16011 - [REG2.068] recursive RefCounted used to work
> https://issues.dlang.org/show_bug.cgi?id=16012 - [REG2.070] forward reference with alias this
> https://issues.dlang.org/show_bug.cgi?id=16013 - [REG2.072a] ICE with mutually dependent structs and alias this

Thank you very much.