Overloaded signature with LiteralString is seen as "broader or same" as str #18584

import os
from typing import TYPE_CHECKING, overload

if TYPE_CHECKING:
    from _typeshed import StrPath
    from typing_extensions import LiteralString, reveal_type

@overload
def insert_before_extension(
    filename: LiteralString | os.PathLike[LiteralString], content: LiteralString
) -> LiteralString: ...
@overload
def insert_before_extension(filename: StrPath, content: str) -> str: ...
def insert_before_extension(filename: StrPath, content: str) -> str:
    """
    Given a filename and some content, insert the content just before
    the extension.

    >>> insert_before_extension('pages.pdf', '-old')
    'pages-old.pdf'
    """
    parts = list(os.path.splitext(filename))
    parts[1:1] = [content]
    return ''.join(parts)

a = insert_before_extension("", "")
reveal_type(a)
b = insert_before_extension(str(0), str(0))
reveal_type(b)