> but errors in DirEntry.is_dir() and DirEntry.is_symlink() 
> are always ignored

In Windows, is_symlink() won't fail due to a long path, since that information comes from the directory listing, but is_dir() might fail for a long path if it's a symlink to a directory. Windows requires that a symlink to a directory is also a directory (i.e. the symlink reparse point is set on an empty directory), but it's not enough to check that it's a directory symlink. is_dir() requires checking that the target exists, which may fail if the path of the link is too long to open and resolve the link target.