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<h2 id="まとめ"><a class="header" href="#まとめ">まとめ</a></h2>
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This chapter covered how to use smart pointers to make different guarantees and
trade-offs than those Rust makes by default with regular references. The
`Box<T>` type has a known size and points to data allocated on the heap. The
`Rc<T>` type keeps track of the number of references to data on the heap so
that data can have multiple owners. The `RefCell<T>` type with its interior
mutability gives us a type that we can use when w