memcpy() comparison: C, Rust, and D

[Nordlöw via Digitalmars-d]

On Tuesday, 31 January 2017 at 19:26:51 UTC, Walter Bright wrote:
> On 1/31/2017 2:44 AM, Nordlöw wrote:
>> On Tuesday, 31 January 2017 at 10:20:59 UTC, Olivier FAURE 
>> wrote:
>>> I thought it meant "the parameter can be returned" not "the 
>>> parameter *will*
>>> be returned".
>>
>> And what about multiple `return`-qualified function parameters?
>
> 'return' means treat the return value "as if" it was derived 
> from that parameter. If multiple parameters are marked as 
> 'return', treat the return value as if it was derived from one 
> of them.
>
> This "as if" thing enables the designer of a function API to 
> set the desired relationships even if the implementation is 
> doing some deviated preversion with the data (i.e. a ref 
> counted object).

Why is this feature used? Optimizations? Safety?