I feel like Rust finally broke the idea that programmers should be in complete control and completely conscious of everything the compiler is doing. It hasn't been that way in decades, compilers are freaking magic. But Rust undid a lot of that with borrowing. People became comfortable with the compiler knowing better than them. I just wish we could relax further: We should never be explicitly iterating forward over a…
Rust is quite transparent in what it does, and is very conservative with compiler magic. The language doesn’t do heap allocations, doesn’t do reference counting, it doesn’t even have implicit numeric type conversion. It won’t implicitly copy types that did not ask to be implicitly copyable, and even that is only legal for types that can be copied with a simple shallow memcpy.
Rust uses zero-cost abstractions all over the place, which means it’s predictable what code they will compile to, and that will be typically something simple. Std types have well-known basic layout, so you know that e.g. iteration over a Vec is going to be a loop incrementing a pointer, and there’s no implicit parallelism.
Describing borrowing as “compiler knowing better than the programmer” is a weird way of looking at it. Borrowing is like type checking. You declare a type to be temporary, and try to use it as long-lived, you get an error. It’s the same as if you declare function to return struct Foo, but returned struct Bar instead. Yes, compiler “knows better than you”, because you just wrote a bug.
Borrowing still compiles to direct pointer usage without a GC (it’s literally guaranteed to be identical to a C pointer in C ABI structs and functions), and you can override lifetimes with unsafe if you think know better than the compiler.