If I create a module X.pmod with the contents
class Y { class X { } }
and then tries to run the following program
class Z { inherit X.Y; }
void main() { }
I will get the error that 'Index Y not present in module "X".' Doing other things with X.Y is however possible, like declaring a variable "X.Y foo;" in the Z class or making the statement werror("%O\n", indices(X.Y)); in main().