[External] : Re: We have to talk about "primitive".

[John Rose]

On 15 Dec 2021, at 15:06, Brian Goetz wrote:

> It took us a while to unravel this one, but I think we did.
> … What this says is that tearing/non-tearing is a property of 
> reference-vs-primitive-ness; accessing a (fat) value through a 
> reference gives you *more guarantees* than accessing it directly. 
> (Correspondingly, this has more costs.)
>
> All of this is to say, as I think you are saying: primitives of a 
> certain size were always tearable, and they still are; references 
> never were, and they are still not.

Of course references don’t tear, and more to the point, `final` fields 
reached by references also don’t tear, because they are (a) safely 
published and (b) never mutated after publication.  So, as Brian says, 
wrapping a reference around some chunks of state has a special benefit 
(as well as a special cost).  The reference wrapper freezes those chunks 
in place, relative to each other.