I'm sure this would be a huge disruption, but I'll throw it out anyway. I'd be perfectly happy if assigning null to a Decimal64/128 container was not allowed, whether it is a reference or a value.
I haven't followed the progress of Valhalla closely. It would be reasonable to delay Decimal64/128 until Valhalla so long as that isn't more than a very few cycles. My concern is that Valhalla is a challenging project. I would not want Decimal64/128 to get hung up because Valhalla is delayed or even worse canceled. Douglas > On Mar 31, 2021, at 8:01 AM, Maurizio Cimadamore > <maurizio.cimadam...@oracle.com> wrote: > > > On 31/03/2021 15:23, Douglas Surber wrote: >> Rather than waiting on Valhala I would prefer that this project be fast >> tracked and added to OpenJDK ASAP. > > There is a catch here. > > While in principle, we can add these as value-based classes, and migrate to > Valhalla later, there is a biggie difference between doing it before/after. > > When it comes to "migrated" primitive classes, there is a choice in how to > interpret the "old" utterances of the class name. Let's say that class Foo is > migrated to be a primitive class; does that mean that all uses of Foo in > existing program will automatically get flattening? Or will references to Foo > be interpreted in a conservative fashion, so as to allow the same operations > as before? One important difference in semantics is assignment to `null` > which is prohibited under flattened semantics, but allowed under "indirect" > (or by reference, if you will) semantics. > > In other words, under the current plan, if Decimal128 is added now and > migrated later, utterances of Decimal128 will behave like they used to > pre-Valhalla, and, to take advantage of flattening you would need to opt-in > with some keyword (e.g. Decimal128.val). > > To me this is kind of a strong argument against going with these classes now > (as much as I understand how useful they'd be even w/o Valhalla) - and > preserving the "good" name (Decimal128) for the flattened case seems worth, > IMHO, waiting few more cycles. > > Maurizio >
