W042 Namespace Cannot Be Default

// Classes A, B and C are in the 
// default namespace. Class D is in
// namespace m. All these classes are
// linked to each other via associations,
// therefore, and because they are not all
// in the same namespace, an import text
// will be generated. However, many programming
// languages do not support import from
// the default namespace so the namespace of
// C will become m because it is linked to
// D, and the same goes for B because C is 
// now in namespace m, and then A is placed 
// in m because B is now in m.

class A{}
class B{*--*A;}
class C{*--* B;}
namespace m;
class D{*--* C;}
namespace -;


// The same issue occurs when an
// entity in a non-default namespace
// extends or implements an entity
// in the default namespace

interface E{}
interface F{isA E;}
interface J{isA F;}
namespace n;
interface K{isA J;}


// Here an import text will be generated for D in X
// because D is in a different namespace
// This feature is not yet supported for interfaces
// and the import text will not be generated for K in Y

namespace p;
class X{isA D;}
// interface Y{isA K;}