Things that keep D from evolving?

[Matt Elkins via Digitalmars-d-learn]

On Friday, 12 February 2016 at 14:03:05 UTC, Steven Schveighoffer 
wrote:
> On 2/10/16 11:51 PM, Matt Elkins wrote:
>
>> * The in keyword. This is nice syntactic sugar over having a 
>> special
>> trait in C++ which deduces whether to pass by value or 
>> const-reference.
>> "foo(in bar)" is way more readable than something like
>> "foo(traits<bar>::fast_param bar)"
>
> Hm... in is short for scope const. It is not pass by reference. 
> Perhaps you meant auto ref?

Right...maybe I've been operating under false pretenses, but I 
was under the impression that the compiler was allowed to 
interpret scope const as either "pass by value" or "pass by const 
reference" freely so long as there was no custom post-blit 
defined? For the purposes of optimization, I mean, to avoid 
needless copying.