Patterns and nulls

[Stephen Colebourne]

On 14 March 2018 at 16:58, Brian Goetz <brian.goetz at oracle.com> wrote:
> Let's assume we have the following declarations:
>
>     record Box(Object);
>     Object o;
>     String s;
>     Box b;
>
> Implicitly, `Box` has a deconstruction pattern whose signature is `Box(out
> Object o)`.
>
> What will users expect on the following?
>
>     Box b = new Box(null);
>     switch (b) {
>         case Box(Candy x): ...
>         case Box(Frog f): ...
>         case Box(Object o): ...
>     }
>
> There are four non-ridiculous possibilities:
>  - NPE
>  - Match none
>  - Match Box(Candy)
>  - Match Box(Object)

If records were changed to not allow null, then `new Box(null)` would
not be possible. Would that not change the line of reasoning here?

Stephen