Target FunctionN, not scala/runtime/java8/JFunction.

We compile FunctionN to Java 8's idea of a function now,
so no need to target the artisanal JFunction and friends,
except when the function is specialized, as I don't yet
see how we can use LMF with the way specialization handles
FunctionN:

First, the working status quo -- the hand-crafted specialized
versions of JFunction0. Notice how `apply$mcB$sp` is looking
pretty SAMmy:

```
@FunctionalInterface
public interface JFunction0$mcB$sp extends JFunction0 {
    @Override
    public byte apply$mcB$sp();

    @Override
    default public Object apply() {
        return BoxesRunTime.boxToByte(this.apply$mcB$sp());
    }
}
```

Contrast this with our specialized standard FunctionN:
```
public interface Function0<R> {
    public R apply();

    default public byte apply$mcB$sp() {
        return BoxesRunTime.unboxToByte(this.apply());
    }
}

public interface Function0$mcB$sp extends Function0<Object> { }
```

The single abstract method in `Function0$mcB$sp` is `apply`, and
the method that would let us avoid boxing, if it were abstract,
is `apply$mcB$sp`...

TODO (after M4):
  - do same for specialized functions (issues with boxing?)
  - remove scala/runtime/java8/JFunction* (need new STARR?)

7 files changed, 18 insertions, 17 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/jvm/CoreBTypes.scala b/src/compiler/scala/tools/nsc/backend/jvm/CoreBTypes.scala
index 696a164c56..ab9fd94a93 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/CoreBTypes.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/CoreBTypes.scala
@@ -219,14 +219,12 @@ class CoreBTypes[BTFS <: BTypesFromSymbols[_ <: Global]](val bTypes: BTFS) {
 
   // enumeration of specialized classes is temporary, while we still use the java-defined JFunctionN.
   // once we switch to ordinary FunctionN, we can use specializedSubclasses just like for tuples.
-  private def functionClasses(base: String): Set[Symbol] = {
-    def primitives = Iterator("B", "S", "I", "J", "C", "F", "D", "Z", "V")
+  private def specializedJFunctionSymbols(base: String): Seq[Symbol] = {
+    def primitives = Seq("B", "S", "I", "J", "C", "F", "D", "Z", "V")
     def ijfd = Iterator("I", "J", "F", "D")
     def ijfdzv = Iterator("I", "J", "F", "D", "Z", "V")
     def ijd = Iterator("I", "J", "D")
-    val classNames = Set.empty[String] ++ {
-      (0 to 22).map(base + _)
-    } ++ {
+    val classNames = {
       primitives.map(base + "0$mc" + _ + "$sp") // Function0
     } ++ {
       // return type specializations appear first in the name string (alphabetical sorting)
@@ -237,7 +235,7 @@ class CoreBTypes[BTFS <: BTypesFromSymbols[_ <: Global]](val bTypes: BTFS) {
     classNames map getRequiredClass
   }
 
-  lazy val srJFunctionRefs: Set[InternalName] = functionClasses("scala.runtime.java8.JFunction").map(classBTypeFromSymbol(_).internalName)
+  lazy val functionRefs: Set[InternalName] = (FunctionClass.seq ++ specializedJFunctionSymbols("scala.runtime.java8.JFunction")).map(classBTypeFromSymbol(_).internalName).toSet
 
   lazy val typeOfArrayOp: Map[Int, BType] = {
     import scalaPrimitives._
@@ -343,7 +341,7 @@ trait CoreBTypesProxyGlobalIndependent[BTS <: BTypes] {
   def srRefConstructors        : Map[InternalName, MethodNameAndType]
   def tupleClassConstructors   : Map[InternalName, MethodNameAndType]
 
-  def srJFunctionRefs: Set[InternalName]
+  def functionRefs: Set[InternalName]
 
   def lambdaMetaFactoryBootstrapHandle  : asm.Handle
   def lambdaDeserializeBootstrapHandle  : asm.Handle
@@ -410,7 +408,7 @@ final class CoreBTypesProxy[BTFS <: BTypesFromSymbols[_ <: Global]](val bTypes:
   def srRefConstructors        : Map[InternalName, MethodNameAndType] = _coreBTypes.srRefConstructors
   def tupleClassConstructors   : Map[InternalName, MethodNameAndType] = _coreBTypes.tupleClassConstructors
 
-  def srJFunctionRefs: Set[InternalName] = _coreBTypes.srJFunctionRefs
+  def functionRefs: Set[InternalName] = _coreBTypes.functionRefs
 
   def srSymbolLiteral           : ClassBType = _coreBTypes.srSymbolLiteral
   def srStructuralCallSite      : ClassBType = _coreBTypes.srStructuralCallSite
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/analysis/BackendUtils.scala b/src/compiler/scala/tools/nsc/backend/jvm/analysis/BackendUtils.scala
index bd7d5d2608..a6b9faa933 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/analysis/BackendUtils.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/analysis/BackendUtils.scala
@@ -125,7 +125,7 @@ class BackendUtils[BT <: BTypes](val btypes: BT) {
 
   private val anonfunAdaptedName = """.*\$anonfun\$\d+\$adapted""".r
   def hasAdaptedImplMethod(closureInit: ClosureInstantiation): Boolean = {
-    isrJFunctionType(Type.getReturnType(closureInit.lambdaMetaFactoryCall.indy.desc).getInternalName) &&
+    isBuiltinFunctionType(Type.getReturnType(closureInit.lambdaMetaFactoryCall.indy.desc).getInternalName) &&
     anonfunAdaptedName.pattern.matcher(closureInit.lambdaMetaFactoryCall.implMethod.getName).matches
   }
 
@@ -250,7 +250,7 @@ class BackendUtils[BT <: BTypes](val btypes: BT) {
     }
   }
 
-  def isrJFunctionType(internalName: InternalName): Boolean = srJFunctionRefs(internalName)
+  def isBuiltinFunctionType(internalName: InternalName): Boolean = functionRefs(internalName)
 
   /**
    * Visit the class node and collect all referenced nested classes.
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/opt/CopyProp.scala b/src/compiler/scala/tools/nsc/backend/jvm/opt/CopyProp.scala
index f1eaebd27c..d28565b9bc 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/opt/CopyProp.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/opt/CopyProp.scala
@@ -296,11 +296,11 @@ class CopyProp[BT <: BTypes](val btypes: BT) {
 
       /**
        * Eliminate the closure value produced by `indy`. If the SAM type is known to construct
-       * without side-effects (e.g. scala/runtime/java8/JFunctionN), the `indy` and its inputs
+       * without side-effects (e.g. scala/FunctionN), the `indy` and its inputs
        * are eliminated, otherwise a POP is inserted.
        */
       def handleClosureInst(indy: InvokeDynamicInsnNode): Unit = {
-        if (isrJFunctionType(Type.getReturnType(indy.desc).getInternalName)) {
+        if (isBuiltinFunctionType(Type.getReturnType(indy.desc).getInternalName)) {
           toRemove += indy
           callGraph.removeClosureInstantiation(indy, method)
           handleInputs(indy, Type.getArgumentTypes(indy.desc).length)
diff --git a/src/compiler/scala/tools/nsc/transform/Delambdafy.scala b/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
index 7ccaec2f50..76c84bd428 100644
--- a/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
+++ b/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
@@ -241,7 +241,7 @@ abstract class Delambdafy extends Transform with TypingTransformers with ast.Tre
           val isSpecialized = specializedName != funSym.name
           val functionalInterface = // TODO: this is no longer needed, right? we can just use the regular function classes
             if (isSpecialized) currentRun.runDefinitions.Scala_Java8_CompatPackage.info.decl(specializedName.prepend("J"))
-            else currentRun.runDefinitions.Scala_Java8_CompatPackage_JFunction(originalFunction.vparams.length)
+            else FunctionClass(originalFunction.vparams.length)
 
           (functionalInterface, isSpecialized)
         }
diff --git a/src/library/scala/collection/mutable/AnyRefMap.scala b/src/library/scala/collection/mutable/AnyRefMap.scala
index 2ed5bbea60..6ff79dd1b8 100644
--- a/src/library/scala/collection/mutable/AnyRefMap.scala
+++ b/src/library/scala/collection/mutable/AnyRefMap.scala
@@ -419,7 +419,11 @@ object AnyRefMap {
   private final val VacantBit  = 0x40000000
   private final val MissVacant = 0xC0000000
 
-  private val exceptionDefault = (k: Any) => throw new NoSuchElementException(if (k == null) "(null)" else k.toString)
+  @SerialVersionUID(1L)
+  private class ExceptionDefault extends (Any => Nothing) with Serializable {
+    def apply(k: Any): Nothing = throw new NoSuchElementException(if (k == null) "(null)" else k.toString)
+  }
+  private val exceptionDefault = new ExceptionDefault
 
   implicit def canBuildFrom[K <: AnyRef, V, J <: AnyRef, U]: CanBuildFrom[AnyRefMap[K,V], (J, U), AnyRefMap[J,U]] =
     new CanBuildFrom[AnyRefMap[K,V], (J, U), AnyRefMap[J,U]] {
diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala
index 72c56def80..8074b448fe 100644
--- a/src/reflect/scala/reflect/internal/Definitions.scala
+++ b/src/reflect/scala/reflect/internal/Definitions.scala
@@ -1567,7 +1567,6 @@ trait Definitions extends api.StandardDefinitions {
       private lazy val PolySigMethods: Set[Symbol] = Set[Symbol](MethodHandle.info.decl(sn.Invoke), MethodHandle.info.decl(sn.InvokeExact)).filter(_.exists)
 
       lazy val Scala_Java8_CompatPackage = rootMirror.getPackageIfDefined("scala.runtime.java8")
-      lazy val Scala_Java8_CompatPackage_JFunction = (0 to MaxFunctionArity).toArray map (i => getMemberIfDefined(Scala_Java8_CompatPackage.moduleClass, TypeName("JFunction" + i)))
     }
   }
 }
diff --git a/test/files/run/t8549.scala b/test/files/run/t8549.scala
index 233a05dee1..e2d0d335b0 100644
--- a/test/files/run/t8549.scala
+++ b/test/files/run/t8549.scala
@@ -79,7 +79,7 @@ object Test extends App {
     }
   }
 
-  // Generated on 20150925-14:41:27 with Scala version 2.12.0-20150924-125956-fd5994f397)
+  // Generated on 20160328-17:47:35 with Scala version 2.12.0-20160328-174205-d46145c)
   overwrite.foreach(updateComment)
 
   check(Some(1))("rO0ABXNyAApzY2FsYS5Tb21lESLyaV6hi3QCAAFMAAF4dAASTGphdmEvbGFuZy9PYmplY3Q7eHIADHNjYWxhLk9wdGlvbv5pN/3bDmZ0AgAAeHBzcgARamF2YS5sYW5nLkludGVnZXIS4qCk94GHOAIAAUkABXZhbHVleHIAEGphdmEubGFuZy5OdW1iZXKGrJUdC5TgiwIAAHhwAAAAAQ==")
@@ -176,7 +176,7 @@ object Test extends App {
   // check(mutable.ArrayBuffer(1, 2, 3))(      "rO0ABXNyACRzY2FsYS5jb2xsZWN0aW9uLm11dGFibGUuQXJyYXlCdWZmZXIVOLBTg4KOcwIAA0kAC2luaXRpYWxTaXplSQAFc2l6ZTBbAAVhcnJheXQAE1tMamF2YS9sYW5nL09iamVjdDt4cAAAABAAAAADdXIAE1tMamF2YS5sYW5nLk9iamVjdDuQzlifEHMpbAIAAHhwAAAAEHNyABFqYXZhLmxhbmcuSW50ZWdlchLioKT3gYc4AgABSQAFdmFsdWV4cgAQamF2YS5sYW5nLk51bWJlcoaslR0LlOCLAgAAeHAAAAABc3EAfgAFAAAAAnNxAH4ABQAAAANwcHBwcHBwcHBwcHBw")
   // TODO SI-8576 Uninitialized field under -Xcheckinit
   // check(mutable.ArraySeq(1, 2, 3))(         "rO0ABXNyACFzY2FsYS5jb2xsZWN0aW9uLm11dGFibGUuQXJyYXlTZXEVPD3SKEkOcwIAAkkABmxlbmd0aFsABWFycmF5dAATW0xqYXZhL2xhbmcvT2JqZWN0O3hwAAAAA3VyABNbTGphdmEubGFuZy5PYmplY3Q7kM5YnxBzKWwCAAB4cAAAAANzcgARamF2YS5sYW5nLkludGVnZXIS4qCk94GHOAIAAUkABXZhbHVleHIAEGphdmEubGFuZy5OdW1iZXKGrJUdC5TgiwIAAHhwAAAAAXNxAH4ABQAAAAJzcQB+AAUAAAAD")
-  check(mutable.AnyRefMap("a" -> "A"))(       "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")
+  check(mutable.AnyRefMap("a" -> "A"))(       "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")
   check(mutable.ArrayStack(1, 2, 3))(       "rO0ABXNyACNzY2FsYS5jb2xsZWN0aW9uLm11dGFibGUuQXJyYXlTdGFja3bdxXbcnLBeAgACSQAqc2NhbGEkY29sbGVjdGlvbiRtdXRhYmxlJEFycmF5U3RhY2skJGluZGV4WwAqc2NhbGEkY29sbGVjdGlvbiRtdXRhYmxlJEFycmF5U3RhY2skJHRhYmxldAATW0xqYXZhL2xhbmcvT2JqZWN0O3hwAAAAA3VyABNbTGphdmEubGFuZy5PYmplY3Q7kM5YnxBzKWwCAAB4cAAAAANzcgARamF2YS5sYW5nLkludGVnZXIS4qCk94GHOAIAAUkABXZhbHVleHIAEGphdmEubGFuZy5OdW1iZXKGrJUdC5TgiwIAAHhwAAAAA3NxAH4ABQAAAAJzcQB+AAUAAAAB")
   check(mutable.DoubleLinkedList(1, 2, 3))( "rO0ABXNyAClzY2FsYS5jb2xsZWN0aW9uLm11dGFibGUuRG91YmxlTGlua2VkTGlzdI73LKsKRr1RAgADTAAEZWxlbXQAEkxqYXZhL2xhbmcvT2JqZWN0O0wABG5leHR0AB5Mc2NhbGEvY29sbGVjdGlvbi9tdXRhYmxlL1NlcTtMAARwcmV2cQB+AAJ4cHNyABFqYXZhLmxhbmcuSW50ZWdlchLioKT3gYc4AgABSQAFdmFsdWV4cgAQamF2YS5sYW5nLk51bWJlcoaslR0LlOCLAgAAeHAAAAABc3EAfgAAc3EAfgAEAAAAAnNxAH4AAHNxAH4ABAAAAANzcQB+AABwcQB+AAtxAH4ACXEAfgAHcQB+AANw")