Reset seen symbols when ending namespace (GH-15244)

Previously, seen symbols were never cleaned during the compilation of a single
file. This makes it impossible to use a class or functi

Reset seen symbols when ending namespace (GH-15244)

Previously, seen symbols were never cleaned during the compilation of a single
file. This makes it impossible to use a class or function from a different
namespace if such a symbol is also declared within the same file. This is
inconsistent with how it would work when split into different files.

show more ...