imo one should always strongly bias/default to unique_ptr, at which point you just can't have circular references. shared_ptr should be used sparingly, not just

imo one should always strongly bias/default to unique_ptr, at which point you just can't have circular references. shared_ptr should be used sparingly, not just because of performance but also as a matter of architecture. You should generally have an organized understanding of ownership, which unique_ptr helps with (and would be the default mode of Rust)