Rant after trying Rust a bit

[Enamex via Digitalmars-d]

On Thursday, 23 July 2015 at 15:03:56 UTC, Dicebot wrote:
> At the same time one HUGE deal breaker with rust traits that 
> rarely gets mentioned is the fact that they are both 
> constraints and interfaces at the same time:
>
> ...
>
> It kills all the necessity for hacks like RangeObject and is 
> quite a salvation once you get to defining dynamic shared 
> libraries with stable ABI.
>
> This is probably my most loved feature of Rust.

Sorry, I don't quite get this. How is the most loved feature of 
Rust (that interfaces are also constraints for generics), a *deal 
breaker*?