It seems there is a contradiction in the C++ 20 Standard relative to the enclosing namespace.
According to the section 9.7.1 Namespace definition of the C++ 20 Standard a namespace definition is a declaration
3 Because a namespace-definition contains declarations in its namespace-body and a namespace-definition is itself a declaration, it follows that namespace-definitions can be nested.
4 The enclosing namespaces of a declaration are those namespaces in which the declaration lexically appears, except for a redeclaration of a namespace member outside its original namespace (e.g., a definition as specified in 220.127.116.11).
8. ...The enclosing namespace set of O is the set of namespaces consisting of the innermost non-inline namespace enclosing an inline namespace O, together with any intervening inline namespaces.
A question arises whether an inline namespace is a declaration?:) Because its enclosing namespace is not the same as the enclosing namespace of a declaration.
I think that the last quote should have some additional clarification words.
With best regards
(Vlad from Moscow)
You can meet me at http://cpp.forum24.ru/ or www.stackoverflow.com or http://ru.stackoverflow.com