The following code does not compile:
> void main() {}
>
> class SuperClass {}
>
> class TemplatedClass(T : SuperClass) {}
>
> class A : SuperClass {
>     alias T = TemplatedClass!B;
> }
>
> class B : SuperClass {
>     alias T = TemplatedClass!C;
> }
>
> class C : SuperClass {}

It gives the error:
> test.d(12): Error: class `test.TemplatedClass(T : SuperClass)` recursive template expansion
> test.d(12):        while looking for match for TemplatedClass!(C)

The aliases do not have to be aliases, as long as there is some reference to the class (e.g. method and variable declarations also work). What exactly is the reason for this error?

On Wednesday, March 21, 2018 00:47:18 Ontonator via Digitalmars-d-learn wrote:
> The following code does not compile:
> > void main() {}
> >
> > class SuperClass {}
> >
> > class TemplatedClass(T : SuperClass) {}
> >
> > class A : SuperClass {
> >
> >     alias T = TemplatedClass!B;
> >
> > }
> >
> > class B : SuperClass {
> >
> >     alias T = TemplatedClass!C;
> >
> > }
> >
> > class C : SuperClass {}
>
> It gives the error:
> > test.d(12): Error: class `test.TemplatedClass(T : SuperClass)`
> > recursive template expansion
> > test.d(12):        while looking for match for
> > TemplatedClass!(C)
>
> The aliases do not have to be aliases, as long as there is some reference to the class (e.g. method and variable declarations also work). What exactly is the reason for this error?

I'm not sure exactly what's happening, since I'm not very familiar with the exactly how template specializations are defined, but the problem clearly relates to the fact that you used a template specialization instead of a template constraint. If you change TemplatedClass to

class TemplatedClass(T)
    if(is(T : SuperClass))
{}

then the code compiles.

- Jonathan M Davis

On 03/21/2018 01:47 AM, Ontonator wrote:
> The following code does not compile:
>> void main() {}
>>
>> class SuperClass {}
>>
>> class TemplatedClass(T : SuperClass) {}
>>
>> class A : SuperClass {
>>     alias T = TemplatedClass!B;
>> }
>>
>> class B : SuperClass {
>>     alias T = TemplatedClass!C;
>> }
>>
>> class C : SuperClass {}
> 
> It gives the error:
>> test.d(12): Error: class `test.TemplatedClass(T : SuperClass)` recursive template expansion
>> test.d(12):        while looking for match for TemplatedClass!(C)
> 
> The aliases do not have to be aliases, as long as there is some reference to the class (e.g. method and variable declarations also work). What exactly is the reason for this error?

Compiler bug. It works when you move the declaration of `B` before the one of `A`. Order shouldn't matter there.

On Wednesday, 21 March 2018 at 06:39:22 UTC, ag0aep6g wrote:
> On 03/21/2018 01:47 AM, Ontonator wrote:
>> The following code does not compile:
>>> [...]
>> 
>> It gives the error:
>>> [...]
>> 
>> The aliases do not have to be aliases, as long as there is some reference to the class (e.g. method and variable declarations also work). What exactly is the reason for this error?
>
> Compiler bug. It works when you move the declaration of `B` before the one of `A`. Order shouldn't matter there.

Is this a known bug, or should I report it?

On Wednesday, March 21, 2018 22:50:32 Ontonator via Digitalmars-d-learn wrote:
> On Wednesday, 21 March 2018 at 06:39:22 UTC, ag0aep6g wrote:
> > On 03/21/2018 01:47 AM, Ontonator wrote:
> >> The following code does not compile:
> >>> [...]
> >>
> >> It gives the error:
> >>> [...]
> >>
> >> The aliases do not have to be aliases, as long as there is some reference to the class (e.g. method and variable declarations also work). What exactly is the reason for this error?
> >
> > Compiler bug. It works when you move the declaration of `B` before the one of `A`. Order shouldn't matter there.
>
> Is this a known bug, or should I report it?

If you can't find it searching on bugzilla, report it.

- Jonathan M Davis

On Wednesday, 21 March 2018 at 23:05:22 UTC, Jonathan M Davis wrote:
> On Wednesday, March 21, 2018 22:50:32 Ontonator via Digitalmars-d-learn wrote:
>> On Wednesday, 21 March 2018 at 06:39:22 UTC, ag0aep6g wrote:
>> > On 03/21/2018 01:47 AM, Ontonator wrote:
>> >> The following code does not compile:
>> >>> [...]
>> >>
>> >> It gives the error:
>> >>> [...]
>> >>
>> >> The aliases do not have to be aliases, as long as there is some reference to the class (e.g. method and variable declarations also work). What exactly is the reason for this error?
>> >
>> > Compiler bug. It works when you move the declaration of `B` before the one of `A`. Order shouldn't matter there.
>>
>> Is this a known bug, or should I report it?
>
> If you can't find it searching on bugzilla, report it.
>
> - Jonathan M Davis

https://issues.dlang.org/show_bug.cgi?id=18646