There are things like RefCell, which enables multiple threads to hold a reference to an object, with run-time checking of borrows. RefCells do not allow multip

There are things like RefCell, which enables multiple threads to hold a reference to an object, with run-time checking of borrows. RefCells do not allow multiple threads to hold a reference to an object because they are not Sync. They only permit dynamic enforcement of Rust's borrowing rules for references, through "interior mutability", as you said.