Jochen, I am a bit skeptical about making changes without clearly understanding exactly what is happening in MC#selectConstructorAndTransformArguments() and why. I don't want to break more than I make there. There are too many small-small bits I don't understand in that method - like the sorting based on type descriptors, role of index of constructor chosen, etc. If I don't clearly get the current picture of it, I will give this issue a pass most probably.
In that case, do you think it will be better to undo 4015 and go back to ClassCastExceptions? Or, can that fix be kept so that at least we are half-way there in supporting this()/super() with non-matching argument/parameter types? It's only in corner cases like var arg usage here that behavior may be buggy until 4016 gets solved properly.
If you think it will be better to go pre-4015 state, I can just undo that for now.