On Wed, May 25, 2016 at 10:30 AM, Joe Watkins <pthre...@pthreads.org> wrote:
> Morning Dmitry, > > > I made this check(s) to be invariant. You may like to do this > differently... > > I think this is what everyone expects, isn't it ? > > I did omit to mention that part ... > > > RFC doesn't define how uninitialized nullable typed properties should > behave. > > It does: > > > *Nullable typed properties will not raise an exception when accessed > before initialization.* > I don't agree with this choice, for three reasons: a) This unnecessarily restricts what can be expressed in the type system. With these semantics it will no longer be possible to express that a property should be nullable, but have no default value. This situation is not uncommon in practice, in particular anytime you have a nullable constructor argument, you will want the corresponding property to be nullable without a default, to ensure that it is explicitly initialized. b) This directly contradicts the meaning of ?Type for parameters. For parameters ?Type means that it's a nullable parameter **without a default value**. That's the very thing that distinguishes it from the Type $prop = null syntax. And now ?Type for properties should mean the exact opposite? c) If you view this in a larger scope of union types, this *special case* becomes even more weird. Why does the particular union Type|null get special treatment, while all other unions don't? Or is it actually not specific to "null", but to single value types? E.g. if we also allowed Type|false, would that also receive an implicit false default value? What about the type null|false? Does that get an implicit default, and if so, which? I realize this is not quite in scope for type properties, but the further evolution of the type system should be kept in mind. Please keep things consistent: If there is not default, there is no default. Nikita
