Bug 6028 – Cannot implicitly convert an array of class to an array of interface

Test case: ---------------------------- interface X {} class K : X {} class L : K {} void main() { L[] x; K[] y = x; // ok X[] z = y; // error } ---------------------------- test.d(8): Error: cannot implicitly convert expression (y) of type K[] to X[] ---------------------------- It should be possible to implicitly convert an array of class to an array of (one of) its base interface type.

Actually, you shouldn't be able to convert either. See issue 2095 Though converting from a class array to an interface array is even worse -- an interface reference is not the same address of a class reference. So this implicit cast would not only have to rewrite all the elements, it would corrupt the original array.