I might be missing something, but what I see as a problem is a situation where: class C implements interfaces IA and IB, which both contain method doSomething() with default implementations, class C doesn't overrides this method, so which implementation is going to be called when method doSomething() will be invoked on instance of C? Will it behave the same way if it is called as instance of C and as instance of IA or IB?
Clearly, there are rules in C++ to handle such situations, one may argue that they are problematic.
If there is no way to break the ambiguity the compilation will fail and you will have to override that method (in 8.4.8.4 of the spec). You can use IA.super or IB.super to call one of the default methods if one of them works for you and you don't need your own bespoke implementation.
Thanks for clarifying; although I don't really like this feature, compilation failure seems to be the best solution (and well I guess I should have RTFM to begin with, sorry).
