diff --git a/internal/util-cache/src/main/scala/sbt/internal/util/Cache.scala b/internal/util-cache/src/main/scala/sbt/internal/util/Cache.scala
index f441fbc20..13710611c 100644
--- a/internal/util-cache/src/main/scala/sbt/internal/util/Cache.scala
+++ b/internal/util-cache/src/main/scala/sbt/internal/util/Cache.scala
@@ -214,14 +214,14 @@ trait UnionImplicits {
         write0(i)
       }
       def equiv: Equiv[Internal] = new Equiv[Internal] {
-        def equiv(a: Internal, b: Internal) =
+        def equiv(a: Internal, b: Internal): Boolean =
           {
             if (a.clazz == b.clazz)
               force(a.cache.equiv, a.value, b.value)
             else
               false
           }
-        def force[T <: UB, UB](e: Equiv[T], a: UB, b: UB) = e.equiv(a.asInstanceOf[T], b.asInstanceOf[T])
+        def force[T <: UB, UB](e: Equiv[T], a: UB, b: UB): Boolean = e.equiv(a.asInstanceOf[T], b.asInstanceOf[T])
       }
     }
 
diff --git a/internal/util-cache/src/main/scala/sbt/internal/util/FileInfo.scala b/internal/util-cache/src/main/scala/sbt/internal/util/FileInfo.scala
index 5f7461eae..1b6ac418c 100644
--- a/internal/util-cache/src/main/scala/sbt/internal/util/FileInfo.scala
+++ b/internal/util-cache/src/main/scala/sbt/internal/util/FileInfo.scala
@@ -10,7 +10,7 @@ import scala.reflect.Manifest
 import sbt.io.Hash
 import sbt.serialization._
 
-sealed trait FileInfo extends NotNull {
+sealed trait FileInfo {
   val file: File
 }
 @directSubclasses(Array(classOf[FileHash], classOf[HashModifiedFileInfo]))
diff --git a/internal/util-collection/src/main/scala/sbt/internal/util/Attributes.scala b/internal/util-collection/src/main/scala/sbt/internal/util/Attributes.scala
index 817896567..25cf298d7 100644
--- a/internal/util-collection/src/main/scala/sbt/internal/util/Attributes.scala
+++ b/internal/util-collection/src/main/scala/sbt/internal/util/Attributes.scala
@@ -89,7 +89,7 @@ object AttributeKey {
     def isLocal: Boolean = true
     def rank = Int.MaxValue
   }
-  private[sbt] final val LocalLabel = "$local"
+  private[sbt] final val LocalLabel = "$" + "local"
 }
 
 /**
diff --git a/internal/util-collection/src/main/scala/sbt/internal/util/KList.scala b/internal/util-collection/src/main/scala/sbt/internal/util/KList.scala
index 5530ba0bc..3406f1b4b 100644
--- a/internal/util-collection/src/main/scala/sbt/internal/util/KList.scala
+++ b/internal/util-collection/src/main/scala/sbt/internal/util/KList.scala
@@ -11,7 +11,7 @@ sealed trait KList[+M[_]] {
   def transform[N[_]](f: M ~> N): Transform[N]
 
   /** Folds this list using a function that operates on the homogeneous type of the elements of this list. */
-  def foldr[T](f: (M[_], T) => T, init: T): T = init // had trouble defining it in KNil
+  def foldr[B](f: (M[_], B) => B, init: B): B = init // had trouble defining it in KNil
 
   /** Applies `f` to the elements of this list in the applicative functor defined by `ap`. */
   def apply[N[x] >: M[x], Z](f: Transform[Id] => Z)(implicit ap: Applicative[N]): N[Z]
@@ -39,7 +39,7 @@ final case class KCons[H, +T <: KList[M], +M[_]](head: M[H], tail: T) extends KL
       np.apply(np.map(g, tt), f(head))
     }
   def :^:[A, N[x] >: M[x]](h: N[A]) = KCons(h, this)
-  override def foldr[T](f: (M[_], T) => T, init: T): T = f(head, tail.foldr(f, init))
+  override def foldr[B](f: (M[_], B) => B, init: B): B = f(head, tail.foldr(f, init))
 }
 sealed abstract class KNil extends KList[Nothing] {
   final type Transform[N[_]] = KNil
diff --git a/internal/util-collection/src/main/scala/sbt/internal/util/PMap.scala b/internal/util-collection/src/main/scala/sbt/internal/util/PMap.scala
index a62755544..989d657e2 100644
--- a/internal/util-collection/src/main/scala/sbt/internal/util/PMap.scala
+++ b/internal/util-collection/src/main/scala/sbt/internal/util/PMap.scala
@@ -87,7 +87,7 @@ abstract class AbstractRMap[K[_], V[_]] extends RMap[K, V] {
  */
 class DelegatingPMap[K[_], V[_]](backing: mutable.Map[K[_], V[_]]) extends AbstractRMap[K, V] with PMap[K, V] {
   def get[T](k: K[T]): Option[V[T]] = cast[T](backing.get(k))
-  def update[T](k: K[T], v: V[T]) { backing(k) = v }
+  def update[T](k: K[T], v: V[T]): Unit = { backing(k) = v }
   def remove[T](k: K[T]) = cast(backing.remove(k))
   def getOrUpdate[T](k: K[T], make: => V[T]) = cast[T](backing.getOrElseUpdate(k, make))
   def mapValue[T](k: K[T], init: V[T], f: V[T] => V[T]): V[T] =
diff --git a/internal/util-collection/src/main/scala/sbt/internal/util/Param.scala b/internal/util-collection/src/main/scala/sbt/internal/util/Param.scala
index 08a58c837..68671c8ca 100644
--- a/internal/util-collection/src/main/scala/sbt/internal/util/Param.scala
+++ b/internal/util-collection/src/main/scala/sbt/internal/util/Param.scala
@@ -9,7 +9,7 @@ import Types._
 trait Param[A[_], B[_]] {
   type T
   def in: A[T]
-  def ret(out: B[T])
+  def ret(out: B[T]): Unit
   def ret: B[T]
 }
 
diff --git a/internal/util-collection/src/main/scala/sbt/internal/util/Settings.scala b/internal/util-collection/src/main/scala/sbt/internal/util/Settings.scala
index 6519287da..a85a3faa6 100644
--- a/internal/util-collection/src/main/scala/sbt/internal/util/Settings.scala
+++ b/internal/util-collection/src/main/scala/sbt/internal/util/Settings.scala
@@ -421,14 +421,10 @@ trait Init[Scope] {
     def dependencies: Seq[ScopedKey[_]]
     def apply[S](g: T => S): Initialize[S]
 
-    @deprecated("Will be made private.", "0.13.2")
-    def mapReferenced(g: MapScoped): Initialize[T]
-    @deprecated("Will be made private.", "0.13.2")
-    def mapConstant(g: MapConstant): Initialize[T]
-
-    @deprecated("Will be made private.", "0.13.2")
-    def validateReferenced(g: ValidateRef): ValidatedInit[T] =
-      validateKeyReferenced(new ValidateKeyRef { def apply[T](key: ScopedKey[T], selfRefOk: Boolean) = g(key) })
+    private[sbt] def mapReferenced(g: MapScoped): Initialize[T]
+    private[sbt] def mapConstant(g: MapConstant): Initialize[T]
+    private[sbt] def validateReferenced(g: ValidateRef): ValidatedInit[T] =
+      validateKeyReferenced(new ValidateKeyRef { def apply[B](key: ScopedKey[B], selfRefOk: Boolean) = g(key) })
 
     private[sbt] def validateKeyReferenced(g: ValidateKeyRef): ValidatedInit[T]
 
@@ -482,14 +478,14 @@ trait Init[Scope] {
     private[sbt] def mapInitialize(f: Initialize[T] => Initialize[T]): Setting[T] = make(key, f(init), pos)
     override def toString = "setting(" + key + ") at " + pos
 
-    protected[this] def make[T](key: ScopedKey[T], init: Initialize[T], pos: SourcePosition): Setting[T] = new Setting[T](key, init, pos)
+    protected[this] def make[B](key: ScopedKey[B], init: Initialize[B], pos: SourcePosition): Setting[B] = new Setting[B](key, init, pos)
     protected[sbt] def isDerived: Boolean = false
     private[sbt] def setScope(s: Scope): Setting[T] = make(key.copy(scope = s), init.mapReferenced(mapScope(const(s))), pos)
     /** Turn this setting into a `DefaultSetting` if it's not already, otherwise returns `this` */
     private[sbt] def default(id: => Long = nextDefaultID()): DefaultSetting[T] = DefaultSetting(key, init, pos, id)
   }
   private[Init] sealed class DerivedSetting[T](sk: ScopedKey[T], i: Initialize[T], p: SourcePosition, val filter: Scope => Boolean, val trigger: AttributeKey[_] => Boolean) extends Setting[T](sk, i, p) {
-    override def make[T](key: ScopedKey[T], init: Initialize[T], pos: SourcePosition): Setting[T] = new DerivedSetting[T](key, init, pos, filter, trigger)
+    override def make[B](key: ScopedKey[B], init: Initialize[B], pos: SourcePosition): Setting[B] = new DerivedSetting[B](key, init, pos, filter, trigger)
     protected[sbt] override def isDerived: Boolean = true
     override def default(_id: => Long): DefaultSetting[T] = new DerivedSetting[T](sk, i, p, filter, trigger) with DefaultSetting[T] { val id = _id }
     override def toString = "derived " + super.toString
@@ -498,7 +494,7 @@ trait Init[Scope] {
   //  This is intended for internal sbt use only, where alternatives like Plugin.globalSettings are not available.
   private[Init] sealed trait DefaultSetting[T] extends Setting[T] {
     val id: Long
-    override def make[T](key: ScopedKey[T], init: Initialize[T], pos: SourcePosition): Setting[T] = super.make(key, init, pos) default id
+    override def make[B](key: ScopedKey[B], init: Initialize[B], pos: SourcePosition): Setting[B] = super.make(key, init, pos) default id
     override final def hashCode = id.hashCode
     override final def equals(o: Any): Boolean = o match { case d: DefaultSetting[_] => d.id == id; case _ => false }
     override def toString = s"default($id) " + super.toString
@@ -547,7 +543,7 @@ trait Init[Scope] {
       case None        => this
       case Some(const) => new Value(() => transform(const))
     }
-    private[sbt] def processAttributes[S](init: S)(f: (S, AttributeMap) => S): S = init
+    private[sbt] def processAttributes[B](init: B)(f: (B, AttributeMap) => B): B = init
   }
   private[this] final class GetValue[S, T](val scopedKey: ScopedKey[S], val transform: S => T) extends Keyed[S, T]
   trait KeyedInitialize[T] extends Keyed[T, T] {
@@ -585,7 +581,7 @@ trait Init[Scope] {
       new Bind[S, T](s => handleUndefined(f(s) validateKeyReferenced g), validIn)
     }
     def mapConstant(g: MapConstant) = new Bind[S, T](s => f(s) mapConstant g, in mapConstant g)
-    private[sbt] def processAttributes[S](init: S)(f: (S, AttributeMap) => S): S = in.processAttributes(init)(f)
+    private[sbt] def processAttributes[B](init: B)(f: (B, AttributeMap) => B): B = in.processAttributes(init)(f)
   }
   private[sbt] final class Optional[S, T](val a: Option[Initialize[S]], val f: Option[S] => T) extends Initialize[T] {
     def dependencies = deps(a.toList)
@@ -599,7 +595,7 @@ trait Init[Scope] {
     def evaluate(ss: Settings[Scope]): T = f(a.flatMap(i => trapBadRef(evaluateT(ss)(i))))
     // proper solution is for evaluate to be deprecated or for external use only and a new internal method returning Either be used
     private[this] def trapBadRef[A](run: => A): Option[A] = try Some(run) catch { case e: InvalidReference => None }
-    private[sbt] def processAttributes[S](init: S)(f: (S, AttributeMap) => S): S = a match {
+    private[sbt] def processAttributes[B](init: B)(f: (B, AttributeMap) => B): B = a match {
       case None    => init
       case Some(i) => i.processAttributes(init)(f)
     }
@@ -633,7 +629,7 @@ trait Init[Scope] {
       {
         val tx = alist.transform(inputs, validateKeyReferencedT(g))
         val undefs = alist.toList(tx).flatMap(_.left.toSeq.flatten)
-        val get = new (ValidatedInit ~> Initialize) { def apply[T](vr: ValidatedInit[T]) = vr.right.get }
+        val get = new (ValidatedInit ~> Initialize) { def apply[B](vr: ValidatedInit[B]) = vr.right.get }
         if (undefs.isEmpty) Right(new Apply(f, alist.transform(tx, get), alist)) else Left(undefs)
       }
 
diff --git a/internal/util-collection/src/main/scala/sbt/internal/util/Signal.scala b/internal/util-collection/src/main/scala/sbt/internal/util/Signal.scala
index 8631fc75b..0c9fac038 100644
--- a/internal/util-collection/src/main/scala/sbt/internal/util/Signal.scala
+++ b/internal/util-collection/src/main/scala/sbt/internal/util/Signal.scala
@@ -31,7 +31,7 @@ object Signals {
       import sun.misc.{ Signal, SignalHandler }
       val intSignal = new Signal(signal)
       val newHandler = new SignalHandler {
-        def handle(sig: Signal) { handler() }
+        def handle(sig: Signal): Unit = { handler() }
       }
       val oldHandler = Signal.handle(intSignal, newHandler)
       object unregisterNewHandler extends Registration {
@@ -74,7 +74,7 @@ private final class Signals0 {
       import sun.misc.{ Signal, SignalHandler }
       val intSignal = new Signal(signal)
       val newHandler = new SignalHandler {
-        def handle(sig: Signal) { handler() }
+        def handle(sig: Signal): Unit = { handler() }
       }
 
       val oldHandler = Signal.handle(intSignal, newHandler)
diff --git a/internal/util-complete/src/main/scala/sbt/internal/util/LineReader.scala b/internal/util-complete/src/main/scala/sbt/internal/util/LineReader.scala
index 712071684..23938b03d 100644
--- a/internal/util-complete/src/main/scala/sbt/internal/util/LineReader.scala
+++ b/internal/util-complete/src/main/scala/sbt/internal/util/LineReader.scala
@@ -52,7 +52,7 @@ abstract class JLine extends LineReader {
     }
   }
 
-  private[this] def resume() {
+  private[this] def resume(): Unit = {
     jline.TerminalFactory.reset
     JLine.terminal.init
     reader.drawLine()
diff --git a/internal/util-complete/src/main/scala/sbt/internal/util/complete/History.scala b/internal/util-complete/src/main/scala/sbt/internal/util/complete/History.scala
index 350c58dfa..d5a96836e 100644
--- a/internal/util-complete/src/main/scala/sbt/internal/util/complete/History.scala
+++ b/internal/util-complete/src/main/scala/sbt/internal/util/complete/History.scala
@@ -7,7 +7,7 @@ package complete
 import History.number
 import java.io.File
 
-final class History private (val lines: IndexedSeq[String], val path: Option[File], error: String => Unit) extends NotNull {
+final class History private (val lines: IndexedSeq[String], val path: Option[File], error: String => Unit) {
   private def reversed = lines.reverse
 
   def all: Seq[String] = lines
diff --git a/internal/util-logging/src/main/scala/sbt/internal/util/StackTrace.scala b/internal/util-logging/src/main/scala/sbt/internal/util/StackTrace.scala
index af16e35d4..e636d914c 100644
--- a/internal/util-logging/src/main/scala/sbt/internal/util/StackTrace.scala
+++ b/internal/util-logging/src/main/scala/sbt/internal/util/StackTrace.scala
@@ -20,7 +20,7 @@ object StackTrace {
     require(d >= 0)
     val b = new StringBuilder()
 
-    def appendStackTrace(t: Throwable, first: Boolean) {
+    def appendStackTrace(t: Throwable, first: Boolean): Unit = {
 
       val include: StackTraceElement => Boolean =
         if (d == 0)
@@ -30,7 +30,7 @@ object StackTrace {
           (_ => { count -= 1; count >= 0 })
         }
 
-      def appendElement(e: StackTraceElement) {
+      def appendElement(e: StackTraceElement): Unit = {
         b.append("\tat ")
         b.append(e)
         b.append('\n')
diff --git a/internal/util-logging/src/main/scala/sbt/util/LogEvent.scala b/internal/util-logging/src/main/scala/sbt/util/LogEvent.scala
index b6225896f..bfc962891 100644
--- a/internal/util-logging/src/main/scala/sbt/util/LogEvent.scala
+++ b/internal/util-logging/src/main/scala/sbt/util/LogEvent.scala
@@ -3,7 +3,7 @@
  */
 package sbt.util
 
-sealed trait LogEvent extends NotNull
+sealed trait LogEvent
 final class Success(val msg: String) extends LogEvent
 final class Log(val level: Level.Value, val msg: String) extends LogEvent
 final class Trace(val exception: Throwable) extends LogEvent
diff --git a/internal/util-logging/src/test/scala/LogWriterTest.scala b/internal/util-logging/src/test/scala/LogWriterTest.scala
index 1f33a3761..4b1aace56 100644
--- a/internal/util-logging/src/test/scala/LogWriterTest.scala
+++ b/internal/util-logging/src/test/scala/LogWriterTest.scala
@@ -103,14 +103,14 @@ object LogWriterTest extends Properties("Log Writer") {
 
 /* Helper classes*/
 
-final class Output(val lines: List[List[ToLog]], val level: Level.Value) extends NotNull {
+final class Output(val lines: List[List[ToLog]], val level: Level.Value) {
   override def toString =
     "Level: " + level + "\n" + lines.map(_.mkString).mkString("\n")
 }
-final class NewLine(val str: String) extends NotNull {
+final class NewLine(val str: String) {
   override def toString = Escape(str)
 }
-final class ToLog(val content: String, val byCharacter: Boolean) extends NotNull {
+final class ToLog(val content: String, val byCharacter: Boolean) {
   def contentOnly = Escape.newline(content, "")
   override def toString = if (content.isEmpty) "" else "ToLog('" + Escape(contentOnly) + "', " + byCharacter + ")"
 }
diff --git a/internal/util-tracking/src/main/scala/sbt/internal/util/ChangeReport.scala b/internal/util-tracking/src/main/scala/sbt/internal/util/ChangeReport.scala
index 10afbea6f..801fc22cf 100644
--- a/internal/util-tracking/src/main/scala/sbt/internal/util/ChangeReport.scala
+++ b/internal/util-tracking/src/main/scala/sbt/internal/util/ChangeReport.scala
@@ -17,7 +17,7 @@ object ChangeReport {
     }
 }
 /** The result of comparing some current set of objects against a previous set of objects.*/
-trait ChangeReport[T] extends NotNull {
+trait ChangeReport[T] {
   /** The set of all of the objects in the current set.*/
   def checked: Set[T]
   /** All of the objects that are in the same state in the current and reference sets.*/
diff --git a/internal/util-tracking/src/main/scala/sbt/internal/util/Tracked.scala b/internal/util-tracking/src/main/scala/sbt/internal/util/Tracked.scala
index 77d4b3a29..e8d3be591 100644
--- a/internal/util-tracking/src/main/scala/sbt/internal/util/Tracked.scala
+++ b/internal/util-tracking/src/main/scala/sbt/internal/util/Tracked.scala
@@ -234,23 +234,23 @@ object FileFunction {
   type UpdateFunction = (ChangeReport[File], ChangeReport[File]) => Set[File]
 
   /**
-    Generic change-detection helper used to help build / artifact generation /
-    etc. steps detect whether or not they need to run. Returns a function whose
-    input is a Set of input files, and subsequently executes the action function
-    (which does the actual work: compiles, generates resources, etc.), returning
-    a Set of output files that it generated.
-
-    The input file and resulting output file state is cached in
-    cacheBaseDirectory. On each invocation, the state of the input and output
-    files from the previous run is compared against the cache, as is the set of
-    input files. If a change in file state / input files set is detected, the
-    action function is re-executed.
-
-    @param cacheBaseDirectory The folder in which to store
-    @param inStyle The strategy by which to detect state change in the input files from the previous run
-    @param outStyle The strategy by which to detect state change in the output files from the previous run
-    @param action The work function, which receives a list of input files and returns a list of output files
-    */
+   * Generic change-detection helper used to help build / artifact generation /
+   * etc. steps detect whether or not they need to run. Returns a function whose
+   * input is a Set of input files, and subsequently executes the action function
+   * (which does the actual work: compiles, generates resources, etc.), returning
+   * a Set of output files that it generated.
+   *
+   * The input file and resulting output file state is cached in
+   * cacheBaseDirectory. On each invocation, the state of the input and output
+   * files from the previous run is compared against the cache, as is the set of
+   * input files. If a change in file state / input files set is detected, the
+   * action function is re-executed.
+   *
+   * @param cacheBaseDirectory The folder in which to store
+   * @param inStyle The strategy by which to detect state change in the input files from the previous run
+   * @param outStyle The strategy by which to detect state change in the output files from the previous run
+   * @param action The work function, which receives a list of input files and returns a list of output files
+   */
   def cached(cacheBaseDirectory: File, inStyle: FilesInfo.Style = FilesInfo.lastModified, outStyle: FilesInfo.Style = FilesInfo.exists)(action: Set[File] => Set[File]): Set[File] => Set[File] =
     cached(cacheBaseDirectory)(inStyle, outStyle)((in, out) => action(in.checked))