so I had never really thought too hard about C++'s unique_ptr abstraction, except to be vaguely annoyed that it so obviously failed to enforce anything remotely resembling what its name appears to promise 1/5
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anyhow, recently I needed to implement a compiler for the language that and I are using for our spring compiler class, and I decided to use C++ and also to take unique_ptr seriously in the implementation 2/5
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the other data structures from the library that I'm using are vector and unordered_map, which I already liked perfectly well, they are both very nice abstractions 3/5
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anyhow, once I understood that unique_ptr meant nothing like its name but rather something like auto_free_pointer, the pieces sort of fell into place and I experienced almost no memory safety bugs while implementing the compiler, nor has afl-fuzz found any so far 4/5
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this is all despite my being a thoroughly mediocre C++ programmer. anyhow this story has no real point except that unique_ptr is actually pretty cool and useful, which I had not expected 5/5
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So good that, in my quite limited understanding of Rust it sounds like everything nontrivial by default is basically a unique_ptr.
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The static enforcement of rules for move semantics and reference aliasing/lifetimes is the interesting part.
Box<T> benefits from those in the same way as any other type. It's quite boring in the Rust world. Any type with a destructor has similar semantics.
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A major difference from C++ in Rust is that assignment, passing and returning values works like C. If the type has a destructor, those have move semantics. A non-trivial copy is done by calling clone explicitly. Rust code uses far more moves and lot more lightweight references.
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Especially slices of strings / vectors. It's too easy to get wrong in C++. The norm in Rust is using &str and &[T] everywhere including slicing into slices. It's normal to make an allocation-free parser, etc. End up avoiding allocation far more than C++ since it's natural + safe.