>From p1240r1.pdf
<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1240r1.pdf> :

  "Of note here is that we are not proposing a function to retrieve members
of namespaces..."

I believe "Automatic Class Register" for load/storing frameworks, may be a
good reason for members of namespace ( obviously filtered ):

I need to get all classes derived from "Widget" (called T in this sample)
in the namespace "MyFramework" and all of it´s inner namespaces, that has
funcion "toStream(ostream&)" declared.


Thanks
BR