Rant after trying Rust a bit

[Tofu Ninja via Digitalmars-d]

On Friday, 24 July 2015 at 19:10:33 UTC, Walter Bright wrote:
> On 7/24/2015 11:42 AM, Jacob Carlborg wrote:
>> I don't see the difference compared to a regular parameter. If 
>> you don't specify
>> any constraints/traits/whatever it like using "Object" for all 
>> your parameter
>> types in Java.
>
> So constraints then will be an all-or-nothing proposition? I 
> believe that would make them essentially useless.
>
> I suspect I am not getting across the essential point. If I 
> have a call tree, and at the bottom I add a call to interface 
> X, then I have to add a constraint that additionally specifies 
> X on each function up the call tree to the root. That is 
> antiethical to writing generic code, and will prove to be more 
> of a nuisance than an asset.
>
> Exactly what sunk Exception Specifications.

But thats exactly how normal interfaces work...

eg:
interface Iface{ void foo(){} }

void func1(Iface x){ func2(x); }
void func2(Iface x){ func3(x); }
void func3(Iface x){ x.bar(); } // ERROR no bar in Iface

Only options here are A: update Iface to have bar() or B: make a 
new interface and change it on the whole tree. The same "problem" 
would exist for the concepts, but its the reason why people want 
it.