With the currently specified semantics, the second pattern is dead,
because switches will only match null at the top level with a case
null. This was an accommodation to clarify that that the null-hostility
of switch is a property of switch, not patterns, and make it more clear
when switch will NPE.
Regardless, what you're asking for is a more precise remainder
checking. The first pattern matches all non-null Foo; because no case
matches null, you're asking that we recognize that there is a dominance
relationship here. This is reasonable to consider (though harder,
because null makes everything harder.)
On 4/18/2022 6:49 PM, Remi Forax wrote:
I've found a way to encode the null pattern if you have a record
record Foo(int x) { }
Foo foo = ...
return switch(foo) {
case Foo(int _) foo -> "i'm a foo not null here !";
case Foo fooButNull -> "i can be only null here !";
};
I wonder if allowing those two patterns, a record pattern and a type pattern
using the same type is a good idea or not, it seems a great way to obfuscate
thing.
Rémi
