Fix lambda inference on openj9 and Java 12 and higher.

[TwilightFlower]

I fixed the problem in my last PR (I feel like I'd fixed that locally and forgot to add it to git, whoops) and also added support for lambda inference on Java 12 and higher by changing the strategy for circumventing access control on those versions.

[LexManos]

Hey, just checking in on this PR, we use this tool in Forge and are running into this issue as well. This change seems to be working. So checking to see if this will be pulled.

[TwilightFlower]

(copy-pasting from commit message since people generally don't read those)
Java 14 changed the way the JVM handles varargs internally, meaning that
new Object[] {...} can't be used as a substitute for varargs on Java 6
source level anymore. However, invokeWithArguments explicitly wants an
Object[], so it works fine on Java 14 while still maintaining Java 6 source compatibility.

[naveenchandra91]

HI @jhalterman : Can we merge this pull request or is there any modifications expected to merge this pull request?

[mkurz]

Ping @jhalterman 😉

[artszko]

Any chances to get this merged in the near future? @jhalterman

[chhsiao90]

Hi @Nuclearfarts ,

I just found it should work with MethodHandles.Lookup to get the override setter. I'm not sure if SharedSecrets is needed to support Java 12 and higher. Maybe it's for supporting openj9?

Here is the minimum code which works all java versions between 9 and 15.

Method privateLookupIn = MethodHandles.class.getMethod("privateLookupIn", Class.class, Lookup.class);
Lookup lookup = (Lookup) privateLookupIn.invoke(null, AccessibleObject.class, MethodHandles.lookup());
MethodHandle overrideSetter = lookup.findSetter(AccessibleObject.class, "override", boolean.class);

Class<?> constantPoolClass = Class.forName("jdk.internal.reflect.ConstantPool");
Method getConstantPool = Class.class.getDeclaredMethod("getConstantPool");
overrideSetter.invoke(getConstantPool, true);
Method getConstantPoolSize = constantPoolClass.getDeclaredMethod("getSize");
overrideSetter.invoke(getConstantPoolSize, true);
Method getConstantPoolMethodAt = constantPoolClass.getDeclaredMethod("getMethodAt", int.class);
overrideSetter.invoke(getConstantPoolMethodAt, true);

[chhsiao90]

I saw the comment #49 (comment)

It's for openj9

[TwilightFlower]

quite honestly i'm not looking at this anymore since we've managed to remove most uses of it.

[mkurz]

@jhalterman Will you make a new release? Does this also fix #52?

[jhalterman]

@mkurz Yes, I just cut a release: 0.6.3. And yes, tests pass on JDK 12 and 14 now, so I've closed #52.

[mkurz]

@jhalterman Fantastic, thanks!