[backport] Accessibility checks for methods with an InvokeDynamic instruction

Implements the necessary tests to check if a method with an
InvokeDynamic instruction can be inlined into a destination class.

Only InvokeDynamic instructions with LambdaMetaFactory as bootstrap
methods can be inlined. The accessibility checks cannot be implemented
generically, because it depends on what the bootstrap method is doing.
In particular, the bootstrap method receives a Lookup object as
argument which can be used to access private methods of the class
where the InvokeDynamic method is located.

A comment in the inliner explains the details.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BackendReporting.scala b/src/compiler/scala/tools/nsc/backend/jvm/BackendReporting.scala
index 4fc05cafdc..4eb24d13e3 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BackendReporting.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BackendReporting.scala
@@ -1,7 +1,7 @@
 package scala.tools.nsc
 package backend.jvm
 
-import scala.tools.asm.tree.{AbstractInsnNode, MethodNode}
+import scala.tools.asm.tree.{InvokeDynamicInsnNode, AbstractInsnNode, MethodNode}
 import scala.tools.nsc.backend.jvm.BTypes.InternalName
 import scala.reflect.internal.util.Position
 import scala.tools.nsc.settings.ScalaSettings
@@ -246,6 +246,11 @@ object BackendReporting {
   case class ResultingMethodTooLarge(calleeDeclarationClass: InternalName, name: String, descriptor: String,
                                      callsiteClass: InternalName, callsiteName: String, callsiteDesc: String) extends CannotInlineWarning
 
+  case object UnknownInvokeDynamicInstruction extends OptimizerWarning {
+    override def toString = "The callee contains an InvokeDynamic instruction with an unknown bootstrap method (not a LambdaMetaFactory)."
+    def emitWarning(settings: ScalaSettings): Boolean = settings.YoptWarningEmitAtInlineFailed
+  }
+
   /**
    * Used in `rewriteClosureApplyInvocations` when a closure apply callsite cannot be rewritten
    * to the closure body method.