On 15/03/2021 13:28, Brian Goetz wrote:
Unchecked conversions are forbidden because of type pollution, that why you can
not write
if (o instanceof Foo<Integer> foo) {
Raw type conversions also leads to type pollution, so i think that a type
pattern with a raw type should be forbidden too.
Note sure I agree here - they are two very different kind of pollutions.
In the Foo<Integer> case the issue is that we might any type that
converts to Foo<Integer> to be treated as a Foo<Integer>. E.g. Foo<?
extends Number> -> Foo<Integer>. That is unsound, and the unsoundness
happens in the conversion itself.
But when you say `o instanceof Foo f`, you are not introducing any
pollution. The pollution will be introduced when (and if) the raw type
will be accessed.
Honestly, I'm not even sure this deserves a warning (other than the
customary "raw-type usage" warning - not an "unchecked" warning, to be
clear).
Maurizio
