[masklinn]

> Given the scope of the project: you guys must be doing something that is so different that it couldn't be rolled into a library

Memory safety and static checking.

> A lot of things are renamed. auto->let, new->box, switch->box You get the feeling that effort was put in to make the language explicitly look different from C++

* let comes from ML and similar languages (e.g. Haskell), which are a huge inspiration of Rust (e.g. the type system). Furthermore, let is not auto, it does pattern matching, it's not just a limited form of type inference (or it'd be after the colon, where the type goes).

* match is much the same, it's a pattern-matching construct not just a jump table

* box is for placement box, IIRC it's similar to a universal placement new. For instance it can be used thus:

    // looks like it returns a basic stack-allocated value
    fn foo() -> int {
        3
    }

    let stack_allocated = foo();
    let heap_allocated = box foo();

  the second one has no more overhead than if the function had returned `box 3` and a ~int (~unique_ptr<int>) in the first place. This also works for structs, the caller can decide where he wants the return value allocated.

[loup-vaillant]

If I had to guess, I'd say "box" is a reference to "boxed values" mentioned in many papers about functional language compilation. Typically, the stack of these implementation would either be "unboxed values", or pointers to "boxes" on the heap.

Clearly, some of those folks have worked on ML or Haskell implementations.

[masklinn]

> If I had to guess, I'd say "box" is a reference to "boxed values"

Yes, that's the start of it but it was expanded to multiple box classes (and maybe eventually user-defined ones) rather than just boxed and unboxed values: a developer can currently use box(HEAP) and box(GC) (a bare `box` is an alias for `box(HEAP)`)