Members of an inline namespace can be used in most respects as though they were members
of the enclosing namespace.
Finally, looking up a name in the
enclosing namespace via explicit qualification ([namespace.qual]
) will include
members of the inline namespace brought in by the using-directive
there are declarations of that name in the enclosing namespace.
These properties are transitive: if a namespace N
contains an inline namespace
, which in turn contains an inline namespace O
, then the members of
can be used as though they were members of M
The enclosing namespace set
is the set of namespaces
consisting of the innermost non-inline namespace enclosing
an inline namespace O
, together with any intervening inline namespaces.