Rust: What is the difference between Cell and RefCell?

Cell — Copy-based interior mutability. RefCell — runtime borrow checking.

Cell:

• No borrow checking.
• For Copy types.
• No runtime overhead.

RefCell:

• Runtime borrow checking.
• For any type.
• Runtime overhead.

1use std::cell::{Cell, RefCell};
2
3let c = Cell::new(5);
4c.set(10);  // No borrow needed
5
6let r = RefCell::new(vec![1, 2, 3]);
7r.borrow_mut().push(4);  // Mutable borrow

Key: Cell for simple Copy types, RefCell for complex types.