JEP 118 works with Lambda ?

[Alex Buckley]

// Adding compiler-dev

Since lambda expressions are expressions, they cannot be reflected over 
directly. However, if you know the method that a lambda expression is 
compiled to, then you can obviously call getParameters() on the 
java.lang.reflect.Method object.

That said, even if you compiled with -parameters, there are bugs in the 
name generation for parameters of the method, so Parameter.getName() 
doesn't work. This has been discussed on compiler-dev and is being fixed 
for JDK 8u20.

Alex

On 4/16/2014 11:43 AM, Luan Cestari wrote:
> Hi, Good morning/afternoon/evening! =)
>
> I got this email from a reply of help at openjdk.java.net ( from
> https://bugs.openjdk.java.net/secure/Dashboard.jspa , where I was thinking
> to create an issue (maybe for enhance or bug, not really sure).
>
> I got a problem during a test using the getName from Parameter (from JEP
> 118, new in Java 8) with Lambda expression (also new in Java 8). I made a
> simple class to reproduce the issue which I posted here
> https://gist.github.com/luan-cestari/10902418 , where the getName works
> fine using other classes like in this other code I made
> https://gist.github.com/luan-cestari/10902332. I started to investigate
> that after I saw a gist ( https://gist.github.com/galdosd/10823529, which
> also created a discussion on
> http://www.reddit.com/r/java/comments/2360is/pretty_map_literals_for_java_8/)
> saying that feature worked fine for him, so I talked with some guys in
> IRC ( OFTC#openjdk ), but we wasn't sure if it is a bug or not.
>
> I searched a bit and I found the following:
>
>     - In http://openjdk.java.net/jeps/118 , it doesnt say about any
>     exception around the Lambda functions
>     - In Oracle documentation it mentions the JVM parameter that have to be
>     used during the compilation to that work fine
>     http://docs.oracle.com/javase/tutorial/reflect/member/methodparameterreflection.html
>     - In javadoc there is no more details about that (I think it could make
>     more clear that there is a JVM parameter or maybe it is possible to have
>     this kind of parameter. Also it could say about execptions such as Lambda
>     expressions)
>     http://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Parameter.html#getName--
>     - I also saw a mail list (
>     http://mail.openjdk.java.net/pipermail/lambda-dev/2013-January/007548.html)
> where Remi and Brian exchanged some mails where he said it is had the
> JEP
>     118 due there are people that want thing in a way and people who doesn't
>     want some changes
>     - In that mail, they cited this document
>     http://cr.openjdk.java.net/~abuckley/8misc.pdf which I think that some
>     parts of it are in JVM spec (
>     - http://docs.oracle.com/javase/specs/ like
>     http://docs.oracle.com/javase/specs/jvms/se8/jvms8.pdf and
>     http://docs.oracle.com/javase/specs/jls/se8/jls8.pdf
>     - ) but it just say the class structure in bytecode, nothing about
>     Lambda and JEP 118
>
> As far as I know, Lambda will create some symbolic invocation using
> invokedynamic which is different than creating anonymous classes, so this
> might be the root cause of the issue. But maybe there is some difference in
> the native implementations (for example, in my case I'm using Fedora 20
> with OpenJDK Runtime Environment (build 1.8.0-b132) / OpenJDK 64-Bit Server
> VM (build 25.0-b70, mixed mode)). In the IRC, people said that maybe the
> IDE was generating the inner classes to make it work, but that would make a
> problem during the runtime if a different tool (like maven) compiles the
> project.
>
> In summary, is the right behavior for JEP 118 return argx due lambda
> expressions? Maybe we could enhance it to make some new features (for Java
> 9 ).
>
> Thank you in advance,
>
> Kindest regards,
>
> Luan Cestari
>
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> exchange for virtue."
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> "At his best, man is the noblest of all animals; separated from law and
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>