[code]
import std.stdio;

interface A { void funcA(); }
class B { final void funcA() { writeln( "B.funcA()" ); } }

class C: B, A { }

void main()
{
    auto c = new C;
    c.funcA();
}
[code/]

$ dmd -run interface.d
interface.d(6): Error: class interface.C interface function 'void funcA()' is not implemented

if swap A and B
[code]
class C: A, B { }
[code/]

$ dmd -run interface.d
interface.d(6): Error: class interface.C base type must be interface, not interface.B

how to workaround this without change in class B and interface A?

On 11/14/2013 01:20 PM, Oleg B wrote:
> [code]
> import std.stdio;
>
> interface A { void funcA(); }
> class B { final void funcA() { writeln( "B.funcA()" ); } }
>
> class C: B, A { }
>
> void main()
> {
>      auto c = new C;
>      c.funcA();
> }
> [code/]
>
> $ dmd -run interface.d
> interface.d(6): Error: class interface.C interface function 'void
> funcA()' is not implemented
>
> if swap A and B
> [code]
> class C: A, B { }
> [code/]
>
> $ dmd -run interface.d
> interface.d(6): Error: class interface.C base type must be interface,
> not interface.B
>
> how to workaround this without change in class B and interface A?

One way is to expose B through 'alias this' (not by inheritance) but it doesn't scale because currently only one 'alias this' is allowed.

import std.stdio;

interface A { void funcA(); }
class B { final void funcA() { writeln( "B.funcA()" ); } }

class C: A {
    B b;
    alias b this;

    this(){
        b = new B();
    }

    void funcA()
    {
        return b.funcA();
    }
}

void main()
{
    auto c = new C;
    c.funcA();
}

Ali

On Thursday, 14 November 2013 at 21:20:57 UTC, Oleg B wrote:
> [code]
> import std.stdio;
>
> interface A { void funcA(); }
> class B { final void funcA() { writeln( "B.funcA()" ); } }
>
> class C: B, A { }
>
> void main()
> {
>     auto c = new C;
>     c.funcA();
> }
> [code/]
>
> $ dmd -run interface.d
> interface.d(6): Error: class interface.C interface function 'void funcA()' is not implemented
>
> if swap A and B
> [code]
> class C: A, B { }
> [code/]
>
> $ dmd -run interface.d
> interface.d(6): Error: class interface.C base type must be interface, not interface.B
>
> how to workaround this without change in class B and interface A?

Try

interface A {
  final void funcA();
}
class B {
  final void funcA() { writeln( "B.funcA()" ); }
}

class C: B, A { }

On Thursday, 14 November 2013 at 21:42:38 UTC, Agustin wrote:
> On Thursday, 14 November 2013 at 21:20:57 UTC, Oleg B wrote:
>> [code]
>> import std.stdio;
>>
>> interface A { void funcA(); }
>> class B { final void funcA() { writeln( "B.funcA()" ); } }
>>
>> class C: B, A { }
>>
>> void main()
>> {
>>    auto c = new C;
>>    c.funcA();
>> }
>> [code/]
>>
>> $ dmd -run interface.d
>> interface.d(6): Error: class interface.C interface function 'void funcA()' is not implemented
>>
>> if swap A and B
>> [code]
>> class C: A, B { }
>> [code/]
>>
>> $ dmd -run interface.d
>> interface.d(6): Error: class interface.C base type must be interface, not interface.B
>>
>> how to workaround this without change in class B and interface A?
>
> Try
>
> interface A {
>   final void funcA();
> }
> class B {
>   final void funcA() { writeln( "B.funcA()" ); }
> }
>
> class C: B, A { }

Oh sorry i mean

interface A {
  void funcA();
}

class B : A {
  final void funcA() { writeln( "B.funcA()" ); }
}

class C : B {
}

On Thursday, 14 November 2013 at 21:45:11 UTC, Agustin wrote:
> On Thursday, 14 November 2013 at 21:42:38 UTC, Agustin wrote:
>> On Thursday, 14 November 2013 at 21:20:57 UTC, Oleg B wrote:
>>> [code]
>>> import std.stdio;
>>>
>>> interface A { void funcA(); }
>>> class B { final void funcA() { writeln( "B.funcA()" ); } }
>>>
>>> class C: B, A { }
>>>
>>> void main()
>>> {
>>>   auto c = new C;
>>>   c.funcA();
>>> }
>>> [code/]
>>>
>>> $ dmd -run interface.d
>>> interface.d(6): Error: class interface.C interface function 'void funcA()' is not implemented
>>>
>>> if swap A and B
>>> [code]
>>> class C: A, B { }
>>> [code/]
>>>
>>> $ dmd -run interface.d
>>> interface.d(6): Error: class interface.C base type must be interface, not interface.B
>>>
>>> how to workaround this without change in class B and interface A?
>>
>> Try
>>
>> interface A {
>>  final void funcA();
>> }
>> class B {
>>  final void funcA() { writeln( "B.funcA()" ); }
>> }
>>
>> class C: B, A { }
>
> Oh sorry i mean
>
> interface A {
>   void funcA();
> }
>
> class B : A {
>   final void funcA() { writeln( "B.funcA()" ); }
> }
>
> class C : B {
> }

we can't change anything in class B

On 2013-11-14 23:17, Oleg B wrote:

>> Oh sorry i mean
>>
>> interface A {
>>   void funcA();
>> }
>>
>> class B : A {
>>   final void funcA() { writeln( "B.funcA()" ); }
>> }
>>
>> class C : B {
>> }
>
> we can't change anything in class B

I would have moved "final void funcA()" to a template and mixin it in both B and C, but if you cannot change B that won't work.

-- 
/Jacob Carlborg

I had thought the pattern

    alias B.funcA funcA;

was supposed to solve things like this, but it does not work.  Any reason it couldn't be made to?  Or, for that matter, why inherited members are not considered by interfaces in the first place?

In related news, if you simply leave A out of C's declaration, then do something like:

    A a = cast(A) c;
    a.funcA();

you will get a segfault.  Hooray.

On Thursday, 14 November 2013 at 21:20:57 UTC, Oleg B wrote:
> [code]
> import std.stdio;
>
> interface A { void funcA(); }
> class B { final void funcA() { writeln( "B.funcA()" ); } }
>
> class C: B, A { }
>
> void main()
> {
>     auto c = new C;
>     c.funcA();
> }
> [code/]
>
> $ dmd -run interface.d
> interface.d(6): Error: class interface.C interface function 'void funcA()' is not implemented
>
> if swap A and B
> [code]
> class C: A, B { }
> [code/]
>
> $ dmd -run interface.d
> interface.d(6): Error: class interface.C base type must be interface, not interface.B
>
> how to workaround this without change in class B and interface A?

This is ambiguous. In one case, from A, you are allowing inheritance and in B you are preventing it.

c.funcA will call the interface version unless you cast to B.

But it should be an easy fix

class C : B, A
{
    void funcA() { ((cast(B))this).funcA(); }
}

This simply redirects funcA(in C, but using interface A) to funcA in B, which is final.