reduce compiler warnings

build.sbt

@@ -686,9 +686,11 @@ lazy val commandProj = (project in file("main-command"))
     testedBaseSettings,
     name := "Command",
     libraryDependencies ++= Seq(launcherInterface, sjsonNewScalaJson.value, templateResolverApi),
+    libraryDependencies ++= (scalaVersion.value match {
+      case v if v.startsWith("2.12.") => List(compilerPlugin(silencerPlugin))
+      case _                          => List()
+    }),
     Compile / scalacOptions += "-Ywarn-unused:-locals,-explicits,-privates",
-    // Removing -Xfatal-warnings is necessary because BasicKeys contains a Key for a deprecated class.
-    Compile / scalacOptions -= "-Xfatal-warnings",
     managedSourceDirectories in Compile +=
       baseDirectory.value / "src" / "main" / "contraband-scala",
     sourceManaged in (Compile, generateContrabands) := baseDirectory.value / "src" / "main" / "contraband-scala",
@@ -863,7 +865,10 @@ lazy val mainProj = (project in file("main"))
         log4jDependencies ++
         Seq(scalaCacheCaffeine, lmCoursierShaded)
     },
-    Compile / scalacOptions -= "-Xfatal-warnings",
+    libraryDependencies ++= (scalaVersion.value match {
+      case v if v.startsWith("2.12.") => List(compilerPlugin(silencerPlugin))
+      case _                          => List()
+    }),
     managedSourceDirectories in Compile +=
       baseDirectory.value / "src" / "main" / "contraband-scala",
     sourceManaged in (Compile, generateContrabands) := baseDirectory.value / "src" / "main" / "contraband-scala",

main-command/src/main/scala/sbt/BasicKeys.scala

@@ -9,6 +9,7 @@ package sbt
 
 import java.io.File
 
+import com.github.ghik.silencer.silent
 import sbt.internal.inc.classpath.{ ClassLoaderCache => IncClassLoaderCache }
 import sbt.internal.classpath.ClassLoaderCache
 import sbt.internal.server.ServerHandler
@@ -34,7 +35,7 @@ object BasicKeys {
     "The function that constructs the command prompt from the current build state.",
     10000
   )
-  val watch =
+  @silent val watch =
     AttributeKey[Watched]("watched", "Continuous execution configuration.", 1000)
   val serverPort =
     AttributeKey[Int]("server-port", "The port number used by server command.", 10000)

main/src/main/scala/sbt/Defaults.scala

@@ -3641,6 +3641,7 @@ object Classpaths {
       ivyRepo.descriptorOptional
     } catch { case _: NoSuchMethodError => false }
 
+  @com.github.ghik.silencer.silent
   private[this] def bootRepository(repo: xsbti.Repository): Resolver = {
     import xsbti.Predefined
     repo match {
@@ -3878,6 +3879,7 @@ trait BuildExtra extends BuildCommon with DefExtra {
     // I tried "Def.spaceDelimited().parsed" (after importing Def.parserToInput)
     // but it broke actions/run-task
     // Maybe it needs to be defined inside a Def.inputTask?
+    @com.github.ghik.silencer.silent
     def inputTask[T](f: TaskKey[Seq[String]] => Initialize[Task[T]]): Initialize[InputTask[T]] =
       InputTask.apply(Def.value((s: State) => Def.spaceDelimited()))(f)
 
@@ -3947,7 +3949,7 @@ trait BuildCommon {
   /**
    * Allows a String to be used where a `NameFilter` is expected.
    * Asterisks (`*`) in the string are interpreted as wildcards.
-   * All other characters must match exactly.  See [[sbt.io.GlobFilter]].
+   * All other characters must match exactly.  See GlobFilter.
    */
   implicit def globFilter(expression: String): NameFilter = GlobFilter(expression)
 

main/src/main/scala/sbt/EvaluateTask.scala

@@ -154,6 +154,7 @@ object EvaluateTask {
   import Keys.state
   import std.Transform
 
+  @com.github.ghik.silencer.silent
   lazy private val sharedProgress = new TaskTimings(reportOnShutdown = true)
   def taskTimingProgress: Option[ExecuteProgress[Task]] =
     if (SysProp.taskTimingsOnShutdown) Some(sharedProgress)

main/src/main/scala/sbt/Main.scala

@@ -200,6 +200,7 @@ object BuiltinCommands {
   def ScriptCommands: Seq[Command] =
     Seq(ignore, exit, Script.command, setLogLevel, early, act, nop)
 
+  @com.github.ghik.silencer.silent
   def DefaultCommands: Seq[Command] =
     Seq(
       multi,

main/src/main/scala/sbt/Plugins.scala

@@ -81,7 +81,7 @@ abstract class AutoPlugin extends Plugins.Basic with PluginsFunctions {
   def trigger: PluginTrigger = noTrigger
 
   /**
-   * This AutoPlugin requires the plugins the [[Plugins]] matcher returned by this method. See [[trigger]].
+   * This AutoPlugin requires the plugins the Plugins matcher returned by this method. See [[trigger]].
    */
   def requires: Plugins = plugins.JvmPlugin
 
@@ -89,20 +89,20 @@ abstract class AutoPlugin extends Plugins.Basic with PluginsFunctions {
 
   override def toString: String = label
 
-  /** The [[Configuration]]s to add to each project that activates this AutoPlugin.*/
+  /** The `Configuration`s to add to each project that activates this AutoPlugin.*/
   def projectConfigurations: Seq[Configuration] = Nil
 
-  /** The [[Setting]]s to add in the scope of each project that activates this AutoPlugin. */
+  /** The `Setting`s to add in the scope of each project that activates this AutoPlugin. */
   def projectSettings: Seq[Setting[_]] = Nil
 
   /**
-   * The [[Setting]]s to add to the build scope for each project that activates this AutoPlugin.
+   * The `Setting` to add to the build scope for each project that activates this AutoPlugin.
    * The settings returned here are guaranteed to be added to a given build scope only once
    * regardless of how many projects for that build activate this AutoPlugin.
    */
   def buildSettings: Seq[Setting[_]] = Nil
 
-  /** The [[Setting]]s to add to the global scope exactly once if any project activates this AutoPlugin. */
+  /** The `Setting`s to add to the global scope exactly once if any project activates this AutoPlugin. */
   def globalSettings: Seq[Setting[_]] = Nil
 
   // TODO?: def commands: Seq[Command]

main/src/main/scala/sbt/internal/BuildStructure.scala

@@ -78,7 +78,7 @@ final class StructureIndex(
  * A resolved build unit.  (`ResolvedBuildUnit` would be a better name to distinguish it from the loaded, but unresolved `BuildUnit`.)
  * @param unit The loaded, but unresolved [[BuildUnit]] this was resolved from.
  * @param defined The definitive map from project IDs to resolved projects.
- *                These projects have had [[Reference]]s resolved and [[AutoPlugin]]s evaluated.
+ *                These projects have had `Reference`s resolved and [[AutoPlugin]]s evaluated.
  * @param rootProjects The list of project IDs for the projects considered roots of this build.
  *                The first root project is used as the default in several situations where a project is not otherwise selected.
  */
@@ -91,7 +91,7 @@ final class LoadedBuildUnit(
 
   /**
    * The project to use as the default when one is not otherwise selected.
-   * [[LocalRootProject]] resolves to this from within the same build.
+   * `LocalRootProject` resolves to this from within the same build.
    */
   val root = rootProjects.headOption.getOrElse(
     throw new java.lang.AssertionError(

main/src/main/scala/sbt/internal/DeprecatedContinuous.scala

@@ -10,11 +10,13 @@ package sbt.internal
 import java.nio.file.Path
 import java.util.concurrent.atomic.AtomicReference
 
+import com.github.ghik.silencer.silent
 import sbt.{ ProjectRef, State, Watched }
 import sbt.internal.io.{ EventMonitor, Source, WatchState => WS }
 import sbt.internal.util.AttributeKey
 import sbt.nio.file.Glob
 
+@silent
 private[internal] trait DeprecatedContinuous {
   protected type StartMessage =
     Option[Either[WS => String, (Int, ProjectRef, Seq[String]) => Option[String]]]
@@ -55,6 +57,8 @@ private[internal] trait DeprecatedContinuous {
     }
   }
 }
+
+@silent
 private[sbt] object DeprecatedContinuous {
   private[sbt] val taskDefinitions = Seq(
     sbt.Keys.watchTransitiveSources := sbt.Defaults.watchTransitiveSourcesTask.value,

main/src/main/scala/sbt/internal/LibraryManagement.scala

@@ -17,8 +17,9 @@ import sbt.util.{ CacheStore, CacheStoreFactory, Logger, Tracked, Level }
 import sbt.io.IO
 import sbt.io.syntax._
 import sbt.Project.richInitializeTask
-import sbt.dsl.LinterLevel.Ignore
 import sjsonnew.JsonFormat
+// This is to turn off "`state` is inside the if expression of a regular task." etc
+import sbt.dsl.LinterLevel.Ignore
 
 private[sbt] object LibraryManagement {
 

main/src/main/scala/sbt/internal/server/LanguageServerReporter.scala

@@ -27,7 +27,7 @@ import scala.collection.JavaConverters._
 import sbt.io.IO
 
 /**
- * Defines a compiler reporter that uses event logging provided by a [[ManagedLogger]].
+ * Defines a compiler reporter that uses event logging provided by a `ManagedLogger`.
  *
  * @param maximumErrors The maximum errors.
  * @param logger The event managed logger.

project/PublishBinPlugin.scala

@@ -16,7 +16,7 @@ object PublishBinPlugin extends AutoPlugin {
   override def globalSettings = Seq(publishLocalBin := (()))
 
   override def projectSettings = Def settings (
-    publishLocalBin := Classpaths.publishTask(publishLocalBinConfig, deliverLocal).value,
+    publishLocalBin := Classpaths.publishTask(publishLocalBinConfig).value,
     publishLocalBinConfig := {
       Classpaths.publishConfig(
         false, // publishMavenStyle.value,

util-tracking/src/main/scala/sbt/util/Tracked.scala

@@ -7,7 +7,7 @@
 
 package sbt.util
 
-import scala.util.{ Failure, Try, Success }
+import scala.util.{ Failure, Try, Success => USuccess }
 
 import java.io.File
 import sbt.io.IO
@@ -182,7 +182,7 @@ object Tracked {
     import CacheImplicits.LongJsonFormat
     def save(store: CacheStore, value: I): Unit = {
       Hasher.hash(value) match {
-        case Success(keyHash) => store.write[Long](keyHash.toLong)
+        case USuccess(keyHash) => store.write[Long](keyHash.toLong)
         case Failure(e) =>
           if (isStrictMode) throw e
           else ()
@@ -191,9 +191,9 @@ object Tracked {
 
     def changed(store: CacheStore, value: I): Boolean =
       Try { store.read[Long] } match {
-        case Success(prev: Long) =>
+        case USuccess(prev: Long) =>
           Hasher.hash(value) match {
-            case Success(keyHash: Int) => keyHash.toLong != prev
+            case USuccess(keyHash: Int) => keyHash.toLong != prev
             case Failure(e) =>
               if (isStrictMode) throw e
               else true