Conversation

Easy to say abstractly, but harder to specify exactly which features you would take out. Practical memory safety without GC requires quite a few moving parts.

Quote Tweet

✕✕✕✕✕

@peterbourgon

Jul 15, 2019

it feels like there’s a smaller language hiding in Rust that’s half as powerful at the edges but 10-50x easier to read, write, and maintain

Replying to

This isn't a Rust subset, but if I were doing memory-safety for a compiled lang, I'd consider making mutability and ability to hold reference/pointer to objects mutually exclusive. Ref tracking then becomes easy without heavy runtime machinery.

Replying to

and

Support for mutable references definitely makes it harder to design a safe language. However, Rust doesn't need any runtime machinery to support either mutable or immutable references. It deals with it by statically preventing the mutable references from overlapping with others.

Replying to

and

Taking an immutable reference prevents modifying the object and taking a mutable reference prevents getting any usable overlapping references. It's definitely very restrictive, and there are alternatives to this design. Rust has Cell and RefCell as library-based alternatives.

Replying to

and

There are clearly ways of doing it differently than Rust though. Many of those different approaches were considered as part of the design. There were a lot of experiments with different approaches and it ended up with the model it did largely due to practical research efforts.

4:11 PM · Jul 15, 2019Twitter Web Client

Replying to

and

For example, it could have had language support for the concept behind the Cell type in the standard library. It would be a lot more flexible as a language implementation rather than built as a crippled library type. I don't think it would be worth having another reference type.