Strange covariant/generics downcasting issue with JDK8

[Vicente-Arturo Romero-Zaldivar]

Hi Mark,

Any javac issue should be submitted to compiler-dev at ... which is the 
correct list for this,

Thanks,
Vicente

On 23/09/13 06:30, 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.
>
> 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);
>
> 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 ( mark at talios.com )
>   — twitter: https://twitter.com/talios
>   — podcast: http://www.illegalargument.com
>   — blog: http://www.theoryinpractice.net
>   — google+: http://gplus.to/talios
>