Introducing Nullable Reference Types in C#. Is there hope for D, too?

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On Tuesday, 21 November 2017 at 01:03:36 UTC, Mark wrote:
> On Monday, 20 November 2017 at 22:56:44 UTC, Walter Bright 
> wrote:
>> On 11/20/2017 3:27 AM, Timon Gehr wrote:
>>> On 20.11.2017 11:07, Atila Neves wrote:
>>>> The problem with null as seen in C++/Java/D is that it's a 
>>>> magical value that different types may have. It breaks the 
>>>> type system.
>>> 
>>> In Java, quite literally so. The Java type system is 
>>> /unsound/ because of null. (I.e. Java is only memory safe 
>>> because it runs on the JVM.)
>>
>> I'm curious. Can you expand on this, please?
>>
>> (In D, casting null to any other pointer type is marked as 
>> @unsafe.)
>
> This blog post seems to summarize the paper he linked to:
> https://dev.to/rosstate/java-is-unsound-the-industry-perspective

And, like clockwork, the very first post is someone complaining 
that he insulted Javascript with an offhand example with a thread 
going 10 posts deep.

I'm not clear on whether he means that Java's type system is 
unsound, or that the type checking algorithm is unsound. From 
what I can tell, he's asserting the former but describing the 
latter.