base_virtual_type_self.nit:44,3: Error: method or variable `a` unknown in `B`.
base_virtual_type_self.nit:45,7: Error: method or variable `a` unknown in `B`.
base_virtual_type_self.nit:46,3: Error: method or variable `a` unknown in `B`.
base_virtual_type_self.nit:47,7: Error: method or variable `a` unknown in `B`.