this(this) must be cheap and O(1)

[Trass3r]

> nothrow guarantees that no Throwables derived from Exception are thrown from a 
> function. OutOfMemoryError is an Error, and Error is _not_ derived from 
> Exception. Errors are expected to be non-recoverable and aren't really meant 
> to be caught.
> 
> So, nothrow has _no_ effect on memory allocations. If it did, nothrow would be 
> pretty useless.

Thx for the explanation.