Convert FunctionBase to Kotlin, add type parameter to Lambda

This will make it possible to avoid raw types when inheriting from both
FunctionBase and Function<R>. This change adds a generic type parameter
to FunctionBase and Lambda which is not source-breaking under our policy
because both FunctionBase and Lambda are internal classes (located in
package kotlin.jvm.internal)

libraries/stdlib/coroutines/jvm/src/kotlin/coroutines/jvm/internal/ContinuationImpl.kt

@@ -132,13 +132,11 @@ internal interface SuspendFunction
 @SinceKotlin("1.3")
 // Restricted suspension lambdas inherit from this class
 internal abstract class RestrictedSuspendLambda(
-    private val arity: Int,
+    public override val arity: Int,
     completion: Continuation<Any?>?
-) : RestrictedContinuationImpl(completion), FunctionBase, SuspendFunction {
+) : RestrictedContinuationImpl(completion), FunctionBase<Any?>, SuspendFunction {
     constructor(arity: Int) : this(arity, null)
 
-    public override fun getArity(): Int = arity
-
     public override fun toString(): String =
         if (completion == null)
             Reflection.renderLambdaToString(this) // this is lambda
@@ -149,16 +147,14 @@ internal abstract class RestrictedSuspendLambda(
 @SinceKotlin("1.3")
 // Suspension lambdas inherit from this class
 internal abstract class SuspendLambda(
-    private val arity: Int,
+    public override val arity: Int,
     completion: Continuation<Any?>?
-) : ContinuationImpl(completion), FunctionBase, SuspendFunction {
+) : ContinuationImpl(completion), FunctionBase<Any?>, SuspendFunction {
     constructor(arity: Int) : this(arity, null)
 
-    public override fun getArity(): Int = arity
-
     public override fun toString(): String =
         if (completion == null)
             Reflection.renderLambdaToString(this) // this is lambda
         else
             super.toString() // this is continuation
-}
+}

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/FunctionBase.kt

@@ -3,10 +3,8 @@
  * that can be found in the license/LICENSE.txt file.
  */
 
-package kotlin.jvm.internal;
+package kotlin.jvm.internal
 
-import kotlin.Function;
-
-public interface FunctionBase extends Function {
-    int getArity();
+interface FunctionBase<out R> : Function<R> {
+    val arity: Int
 }

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/Lambda.kt

@@ -7,8 +7,6 @@ package kotlin.jvm.internal
 
 import java.io.Serializable
 
-abstract class Lambda(private val arity: Int) : FunctionBase, Serializable {
-    override fun getArity(): Int = arity
-
+abstract class Lambda<out R>(override val arity: Int) : FunctionBase<R>, Serializable {
     override fun toString(): String = Reflection.renderLambdaToString(this)
 }

libraries/stdlib/jvm/src/kotlin/coroutines/experimental/jvm/internal/CoroutineImpl.kt

@@ -18,7 +18,7 @@ abstract class CoroutineImpl(
     arity: Int,
     @JvmField
     protected var completion: Continuation<Any?>?
-) : Lambda(arity), Continuation<Any?> {
+) : Lambda<Any?>(arity), Continuation<Any?> {
 
     // label == -1 when coroutine cannot be started (it is just a factory object) or has already finished execution
     // label == 0 in initial part of the coroutine