AssertionError when using anonymous namespaces

[IcarusCoding]

When using anonymous namespaces like:

namespace {
constexpr std::string_view test{"test"};
}

I get the following error:

[...] WARNING: Error in type declaration.
If typedef-like declaration:
  Type must be either just a name or a typedef-like declaration.
  If just a name:
    Error in declarator or parameters-and-qualifiers
    Invalid C++ declaration: Expected identifier in nested name. [error at 0]
      
      ^
  If typedef-like declaration:
    Invalid C++ declaration: Expected identifier in nested name. [error at 0]
      
      ^
If type alias or template alias:
  Invalid C++ declaration: Expected identifier in nested name. [error at 0]
    
    ^

Exception occurred:
  File "/usr/lib/python3/dist-packages/breathe/renderer/sphinxrenderer.py", line 710, in handle_declaration
    assert isinstance(n, addnodes.desc_sig_keyword)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError

The following works though:

namespace test {
namespace {
constexpr std::string_view test{"test"};
}
}

Environment:

Platform:              linux; (Linux-6.8.0-51-generic-x86_64-with-glibc2.39)
Python version:        3.12.3 (main, Jan 17 2025, 18:03:48) [GCC 13.3.0])
Python implementation: CPython
Sphinx version:        7.2.6
Docutils version:      0.20.1
Jinja2 version:        3.1.2
Pygments version:      2.17.2
Breathe version:       4.35.0
Doxygen version:       1.9.8