namespaces user overloading c++

when authoring library sole namespace, it's mostly accessible yield overloaded operators classes namespace. seems (at slightest g++) overloaded operators implemented presumably library's namespace:

namespace lib {
class {
};

a operator+(const a&, const a&);
} // namespace lib

or tellurian namespace

namespace lib {
class {
};
} // namespace lib

lib::a operator+(const lib::a&, const lib::a&);

from testing, both seem work fine. there any receptive inadequacy between twin options? presumably proceed better?