ClassCastException on collection generics for jdk8 working code

[Martijn Verburg]

Hi Emanuel,

Good to see you today! OpenJDK mailing lists strip attachments so you'll
need to give a pastebin link or similar.

Cheers,
Martijn

On 17 January 2015 at 16:58, Emanuel <emanuele.tagliaferri at gmail.com> wrote:

> I am at the Adopt OpenJdk hack day organized by the LJC, I am running
> tests cases of OrientDB (open source java based NoSql) on JDK9 (Build
> b45 ), and i got some issue with the use of generics.
>
> basically this code:
>         List<Date> list = new ArrayList<>();
>         list.add(new Date());
>
>         List<Foo> cList = (List<Foo>) (List<?>) list;
>         Date date = (Date) cList.get(0);                        // it
> fail here
>
> on jdk8 it work fine, on jdk9 the code fail in the marked line.
>
> the jdk8 bytecode for the failing line is:
>       invokeinterface #7,  2            // InterfaceMethod
> java/util/List.get:(I)Ljava/lang/Object;
>       checkcast     #4                  // class java/util/Date
>
> instead of  on jdk9 is:
>       invokeinterface #7,  2            // InterfaceMethod
> java/util/List.get:(I)Ljava/lang/Object;
>       checkcast     #8                  // class ListFail$Foo
>       checkcast     #4                  // class java/util/Date
>
>
> and is clear that there's a additional cast that is causing the exception.
>
> I understand that this code is not the exactly clean and correct
> conceptually, but it may be a lot of this staff out there that can be
> break by jdk9.
>
> In attachment a couple of simple example for reproduce this issue.
>
>
> Regards
>
> Emanuel
>
>
>