Strange covariant/generics downcasting issue with JDK8

[Vicente-Arturo Romero-Zaldivar]

Hi Mark,

On 23/09/13 09:30, Mark Derricutt wrote:
> Hi all,
>
> Since you're all enjoying JavaOne at the moment I was thinking it was 
> about time that I starting building $work's project under JDK8 and 
> give it some love over my normal small projects and ran into an odd 
> issue with generics/covariant returns that works fine under 7u40 and 
> breaks under 8DP.

Not all of us ;)

>
> I've extracted this into a simple project [1] which I've pushed to 
> github, I've added a comment on the code that breaks under JDK8.
>
> The code in question is:
>
> List<Strings> strings…
>
> assertThat(strings).describedAs("test")
>   .isNotEmpty()
>   .has(regexMatch("th.*"))
>   .doesNotHave(regexMatch("moo.*"))
>   .hasSize(3);

I would appreciate if you can send a standalone program reproducing the bug.

Thanks in advance,

Vicente

>
> When calling assertThat(strings) a class of type ListAssertion is 
> returned, and passed along the call chain.
>
> The problem appears to be that when doesNotHave() returns, javac no 
> longer sees a ListAssertion but rather a top level AbstractAssertion 
> on which doesNotHave is defined:
>
>   /** {@inheritDoc} */
>   public S has(Condition<? super A> condition) {
>     conditions.assertHas(info, actual, condition);
>     return myself;
>   }
>
>   /** {@inheritDoc} */
>   public S doesNotHave(Condition<? super A> condition) {
>     conditions.assertDoesNotHave(info, actual, condition);
>     return myself;
>   }
>
> Now, both has() and doesNotHave() appear to have the exact same 
> signature, yet commenting out the call to doesNotHave() doesn't appear 
> to trigger what appears to be a down casting to AbstractAssertion 
> which doesn't include a method called hasSize(), the output I see from 
> javac is:
>
> ~/D/covariantfail (master|…) $ 
> /Library/Java/JavaVirtualMachines/jdk1.8.0.jdk/Contents/Home/bin/java 
> -version
> java version "1.8.0-ea"
> Java(TM) SE Runtime Environment (build 1.8.0-ea-b106)
> Java HotSpot(TM) 64-Bit Server VM (build 25.0-b48, mixed mode)
>
> ~/D/covariantfail (master|…) $ 
> /Library/Java/JavaVirtualMachines/jdk1.8.0.jdk/Contents/Home/bin/javac 
> -version
> javac 1.8.0-ea
>
> /Library/Java/JavaVirtualMachines/jdk1.8.0.jdk/Contents/Home/bin/javac 
> -d /Users/amrk/Dropbox/covariantfail/target/test-classes -classpath 
> /Users/amrk/Dropbox/covariantfail/target/test-classes:/Users/amrk/Dropbox/covariantfail/target/classes:/Users/amrk/.m2/repository/org/testng/testng/6.8.5/testng-6.8.5.jar:/Users/amrk/.m2/repository/junit/junit/4.10/junit-4.10.jar:/Users/amrk/.m2/repository/org/hamcrest/hamcrest-core/1.1/hamcrest-core-1.1.jar:/Users/amrk/.m2/repository/org/beanshell/bsh/2.0b4/bsh-2.0b4.jar:/Users/amrk/.m2/repository/com/beust/jcommander/1.27/jcommander-1.27.jar:/Users/amrk/.m2/repository/org/yaml/snakeyaml/1.6/snakeyaml-1.6.jar:/Users/amrk/.m2/repository/org/easytesting/fest-assert-core/2.0M10/fest-assert-core-2.0M10.jar:/Users/amrk/.m2/repository/org/easytesting/fest-util/1.2.5/fest-util-1.2.5.jar: 
> -sourcepath /Users/amrk/Dropbox/covariantfail/src/test/java: 
> /Users/amrk/Dropbox/covariantfail/src/test/java/com/talios/RegexMatch.java 
> /Users/amrk/Dropbox/covariantfail/src/test/java/com/talios/AppTest.java -g 
> -nowarn -target 1.5 -source 1.5 -encoding UTF-8
> /Users/amrk/Dropbox/covariantfail/src/test/java/com/talios/AppTest.java:37: 
> error: cannot find symbol
>                 .hasSize(3);
>                 ^
>   symbol:   method hasSize(int)
>   location: class AbstractAssert
> Note: 
> /Users/amrk/Dropbox/covariantfail/src/test/java/com/talios/AppTest.java uses 
> unchecked or unsafe operations.
> Note: Recompile with -Xlint:unchecked for details.
> 1 error
>
>
> Is this a known bug in the JDK at all? I'm quite surprised no one else 
> has hit something like this before if its not?
>
>
>
>
> [1] https://github.com/talios/jdk8-covariantfail
> [2] 
> https://github.com/talios/jdk8-covariantfail/commit/faa016e57f754230da46e3453b964d497ec065b5#commitcomment-4151896
>
>
> --
> Mark Derricutt <mailto:mark at talios.com> — twitter 
> <https://twitter.com/talios> — podcast 
> <http://www.illegalargument.com/> — blog 
> <http://www.theoryinpractice.net/> — google+ <http://gplus.to/talios>
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.openjdk.java.net/pipermail/compiler-dev/attachments/20130926/aac26917/attachment.html