Anyone know why there isn't a single type/interface that allows for consumers to supply any of Arc, Rc etc boxed values?

I haven't investigated it deeply, but I was developing something in Rust, and whether something needs to be threadsafe or not is entirely on the consumer's use case... bad separation of concerns for the provider of a generic interface to have to specify the specific type of boxed value. 100% fine if the behavior in this case is to pre-allocate the max possible boxed type memory requirement.

This is the only thing I was really frustrated with in Rust