Comment by verdagon
3 years ago
Author here, Cone is a pretty fascinating language.
It builds a borrow checker on top of any user-specified allocator, whether that be single ownership, reference counting, arenas, garbage collection, or any other user-specified strategy. A user can even code their own.
It's a very promising approach, because it preserves the borrow checker's strengths while addressing its the borrow checker's development velocity downsides. GC and RC often make a program's overall architecture looser and more flexible, but by offering borrow checking for everything else, it allows a program to much more cut down on its memory safety overhead.
What Cone does differently than other languages is that it decouples the allocation strategy from the type of data you're working with. This makes it much easier to change your code to use different memory safety styles. In a way, it's like Rust but allows for more flexibility on memory management.
It's still in progress, but I encourage anyone interested in languages and memory safety to take a look: https://cone.jondgoodwin.com/
User-specified local allocators are planned for Rust too. Among other things, they're needed for feature parity with C++.
Technically it’s only the standard library that lacks custom allocator support. Box and Vec and all the rest are “just” types defined in the standard library, and if you define your own, you can use any allocator you want and still take advantage of the borrow checker and other language features. This has been possible since 1.0.
…Well, except for certain magic features that the standard library types get that you can’t (yet) replicate in a custom type. This is an annoying wart, but they’re relatively minor.
But yeah, custom allocator support for standard library containers is planned.
I recommend taking a look at Cone in a little more detail, its type system support for allocators are head and shoulders above what Rust has. The language's awareness of allocator allows it to decouple it from the users code in a way no other language allows (except perhaps Odin).
>"feature parity with C++"
I think Rust is missing a fair bit more than "user-specified local allocators" to be on feature parity with C++. Curious if it plans to be on full feature parity.
It definitely misses some features that are considered bad: e.g implementation inheritance or memory handling by exceptions. Those are not essential for anything and are not planned.
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