Rant after trying Rust a bit

[Andrei Alexandrescu via Digitalmars-d]

On 7/23/15 5:07 AM, Walter Bright wrote:
> On 7/22/2015 11:47 PM, Jacob Carlborg wrote:
>> On 2015-07-22 20:47, simendsjo wrote:
>>
>>> Traits
>>> ------
>>> I think the ability to express an interface without buying into
>>> inheritance is the right move. The alternative in D is specifying the
>>> behavior as a template
>>
>> I completely agree and don't really like the approach D has
>> implemented template
>> constraints. Yeah I know, Andrei will destroy this :)
>
> Consider that template constraints can be arbitrarily complex, and can
> even check behavior, not just a list of function signatures ANDed
> together. Turns out many constraints in Phobos are of the form (A || B),
> not just (A && B).

Agreed. And that's just scratching the surface.

Serious question: how do you express in Rust that a type implements one 
trait or another, then figure out statically which?

>  >> and verifying the contract in a unittest for the type.
>
> I am a bit puzzled by the notion of shipping template code that has
> never been instantiated as being a positive thing. This has also turned
> up in the C++ static_if discussions.

This is easy to understand. Weeding out uncovered code during 
compilation is a central feature of C++ concepts. Admitting you actually 
never want to do that would be a major blow.


Andrei