True Duck typization.

Now we have "duck typization":

interface IDuck {
    void Quack();
}
class DuckTypedDuck : IDuck {
    void Quack() { }
}
class ImplicitlyTypedDuck : IDuck {
    void IDuck.Quack() { }
}
class DuckInTheShadow {
    void Quack() { }
}

There DuckInTheShadow is not an IDuck.

---

I want for DuckInTheShadow is an IDuck.

For example:

interface IDuck {
    void Quack();
}
class Animal {
    void Bark() { }
}
class DuckInTheShadow : Animal {
    void Quack() { }
}

interface IDartDuck {
    void Quack();
}
class DuckInTheDart : IDartDuck {
    void IDartDuck.Quack() { }
}

class Program {
    void Main () {
        var duckInTheShadow = new DuckInTheShadow();
        IsAnimalAnIDuck(duckInTheShadow); // return false
        IsDuckInTheShadowAnIDuck(duckInTheShadow); // return true

        var duckInTheDart = new DuckInTheDart();
        IsDuckInTheDartAnIDuck(duckInTheDart); // return false
                                               // because class can have multiple implicit
                                               // `void Quack();` method realizations
                                               // from different interfaces
                                               // 
                                               // if class implements `IDuck` or
                                               // inherits `IDuck` implementation
                                               // it is already `IDuck`
        IsIDartDuckAnIDuck(duckInTheDart); // return true
    }
    bool IsAnimalAnIDuck (Animal animal) {
        return animal is IDuck;
    }
    bool IsDuckInTheShadowAnIDuck(DuckInTheShadow duckInTheShadow) {
        return duckInTheShadow is IDuck;
    }
    bool IsDuckInTheDartAnIDuck(DuckInTheDart duckInTheDart) {
        return duckInTheDart is IDuck;
    }
    bool IsIDartDuckAnIDuck(IDartDuck dartDuck) {
        return dartDuck is IDuck;
    }
}

---

It must work in compile time first.
For runtime duck typing can be used dynamic<IDuck>.

[narmontas]

Isn't ImplicitlyTypedDuck explicitly implemented?

[davidfowl]

Sounds like you're asking for compiler features? Try https://github.com/dotnet/roslyn

@narmontas , yes