Linguistic tool lupdate failed to extract string context

The linguistic tool "lupdate" couldn't correctly extract string context in source file; source file uses "using namespace A::B..." instead of declaring each namespace like:"

namespace A {
namespace B{
...
class classA
}
}

Another comment has been added at the top of the source file:

/*
TRANSLATOR A::B::...classA
*/

based on this article: 

https://doc.qt.io/archives/qt-4.8/linguist-programmers.html

The expected behavior should be that the string wrapped by "tr" function is extracted with its namespaces as prefix, like

<context>
  <name>A::B::...classA</name>
</context>

The actual behavior missed namespaces, which is:

<context>
 <name>classA</name>
</context>

During string harvesting step, warnings like below keeps pop up:

xxx.cpp: LINE-NUMBER: Qualifying with unknown namespace/class ::classA

As the result, when applying localization step, strings couldn't be correctly get replaced with localized string.