Inherent code performance advantages of D over C?

[jerro]

> You, as the guy who wrote the code, will (or should) know that 
> there are no other live references, hence you are telling the 
> compiler "trust me, I know there aren't any".

So, is the intended meaning the following: If there exist any 
immutable references to the data, mutating it results in 
undefined behavior? If so, I think the documentation on creating 
immutable data should explicitly say so.