Describe the bug

The simple

.. py.function:: func(*args: *tuple[str, int])

emits a warning

WARNING: could not parse arglist ('*args: *tuple[int, str]'): Unable to parse Starred object

The culprit is the absence of a visit_Starred method in the class sphinx.pycode.ast._UnparseVisitor. After fixing that with the inclusion of

def visit_Starred(self, node: ast.Starred) -> str:
    return f'*{self.visit(node.value)}'

a further warning is emitted:

WARNING: py:class reference target not found: *tuple[int, str] [ref.class]

In this case the problem is that sphinx.domains.python._annotations._parse_annotation tries to find a cross-reference without first splitting off the star in front. A solution is the inclusion of the following block in the body of the unparse function within that function:

if isinstance(node, ast.Starred):
    result = [addnodes.desc_sig_operator('', '*')]
    result.extend(unparse(node.value))
    return result

PR to follow.

How to Reproduce

index.rst:

.. py.function:: func(*args: *tuple[str, int]

conf.py:

extensions = [
    "sphinx.ext.intersphinx",
]
intersphinx_mapping = {
    "python": ("https://docs.python.org/3/", None),
}

Environment Information

Platform:              darwin; (macOS-14.7-arm64-arm-64bit-Mach-O)
Python version:        3.13.1 (main, Dec  3 2024, 17:59:52) [Clang 15.0.0 (clang-1500.3.9.4)])
Python implementation: CPython
Sphinx version:        8.2.0
Docutils version:      0.21.2
Jinja2 version:        3.1.5
Pygments version:      2.19.1

Sphinx extensions

["sphinx.ext.intersphinx"]

Additional context

None.