Compiler support for JEP-193 VarHandle polymorphic signatures

[retronym]

VarHandles bring a host of new "polymorphic signature" methods to
the Java 9 standard library. This commit updates the way we detect
such methods to look at the absense/presense of the
PolymorphicSignature annotation, so as to include these (and any
future additions.)

When we see applications of such methods, we disable adaptation
of argument and return types.

Tested manually with JDK9-ea:

Welcome to Scala 2.12.2-20161208-165912-3de1c0c (Java HotSpot(TM) 64-Bit Server VM, Java 9-ea). Type in expressions for evaluation. Or try :help. scala> import java.lang.invoke._, scala.runtime.IntRef import java.lang.invoke._ import scala.runtime.IntRef scala> val varHandle = MethodHandles.lookup().in(classOf[IntRef]).findVarHandle(classOf[IntRef], "elem", classOf[Int]); varHandle: java.lang.invoke.VarHandle = java.lang.invoke.VarHandleInts$FieldInstanceReadWrite@7112ce6 scala> varHandle.getAndSet(ref, 1): Int res5: Int = 0 scala> varHandle.getAndSet(ref, 1): Int res6: Int = 1 

Inspecting bytecode shows the absense of box/unboxing:

object Test { import java.lang.invoke._, scala.runtime.IntRef val varHandle = MethodHandles.lookup().in(classOf[IntRef]).findVarHandle(classOf[IntRef], "elem", classOf[Int]); def main(args: Array[String]): Unit = { val i : Int = varHandle.getAndSet(IntRef.zero, 1) } } 

 public void main(java.lang.String[]); Code: 0: aload_0 1: invokevirtual #28 // Method varHandle:()Ljava/lang/invoke/VarHandle; 4: invokestatic #34 // Method scala/runtime/IntRef.zero:()Lscala/runtime/IntRef; 7: iconst_1 8: invokevirtual #40 // Method java/lang/invoke/VarHandle.getAndSet:(Lscala/runtime/IntRef;I)I 11: istore_2 12: return 

Reference scala/scala-dev#139

[retronym]

Review by @lrytz

[lrytz]

tiny cleanup, then 🚢 it

!! 1264 - run/t6240-universe-code-gen.scala [non-zero exit code] ##### Log file '/home/jenkins/workspace/scala-2.12.x-validate-test/test/files/run/t6240-universe-code-gen-run.log' from failed test ##### java.lang.AssertionError: assertion failed: /home/jenkins/workspace/scala-2.12.x-validate-test/src/reflect/scala/reflect/runtime/JavaUniverseForce.scala must be updated. =========================================================== DIFF: =========================================================== --- a +++ b @@ -268,2 +268,3 @@ definitions.RepeatedParamClass + definitions.JavaLangInvokePackage definitions.ConsClass