Enable -Xlint and -Werror

Linting on 2.13 such as required empty args,
inferred Any in sameElements of Array[_],
Timeout is double-valued, avoid Any.equals,
some elements unused, deprecations.
Allow JavaConverters.

Can't use nowarn and unused annotations
under 2.11/2.12.

build.sbt

@@ -41,11 +41,11 @@ mimaPreviousArtifacts := Set.empty
 crossScalaVersions := List()
 addCommandAlias(
   "scalafixAll",
-  "; ++2.12.10 ; scalafixEnable ; all scalafix test:scalafix"
+  s"; ++$scala212 ; scalafixEnable ; all scalafix test:scalafix"
 )
 addCommandAlias(
   "scalafixCheckAll",
-  "; ++2.12.10 ;  scalafixEnable ; scalafix --check ; test:scalafix --check"
+  s"; ++$scala212 ;  scalafixEnable ; scalafix --check ; test:scalafix --check"
 )
 val isPreScala213 = Set[Option[(Long, Long)]](Some((2, 11)), Some((2, 12)))
 val scala2Versions = List(scala213, scala212, scala211)
@@ -152,17 +152,28 @@ val sharedSettings = List(
           "-Ywarn-unused-import",
           "-target:jvm-1.8"
         )
-      case Some((major, _)) if major != 2 =>
+      case Some((2, 12)) =>
         List(
-          "-language:implicitConversions"
+          "-feature",
+          "-target:jvm-1.8",
+          "-Ywarn-unused-import",
+          "-Yrangepos"
         )
-      case _ =>
+      case Some((2, _)) =>
         List(
+          "-feature",
           "-target:jvm-1.8",
-          "-Yrangepos",
-          // -Xlint is unusable because of
-          // https://github.com/scala/bug/issues/10448
-          "-Ywarn-unused:imports"
+          "-Wconf:cat=deprecation&msg=JavaConverters:s",
+          raw"-Wconf:cat=deprecation&site=munit\.internal\.MacroCompatScala2\..*:s",
+          "-Wconf:cat=unused-privates&msg=never used:s",
+          "-Wconf:cat=unused-params&msg=never used:s",
+          //"-Werror",
+          "-Xlint",
+          "-Yrangepos"
+        )
+      case _ =>
+        List(
+          "-language:implicitConversions"
         )
     }
   }

docs/tests.md

@@ -161,7 +161,7 @@ def check[T](
 
 check("basic", List(1, 2), Some(1))
 check("empty", List(), Some(1))
-check("null", List(null, 2), Some(null))
+check("null", List(null, "more"), Some(null))
 ```
 
 When declaring tests in a helper function, it's useful to pass around an

munit-scalacheck/shared/src/main/scala/munit/ScalaCheckSuite.scala

@@ -1,5 +1,7 @@
 package munit
 
+import language.implicitConversions
+
 import org.scalacheck.Prop
 import org.scalacheck.{Test => ScalaCheckTest}
 import org.scalacheck.util.Pretty

munit/js/src/main/scala/munit/internal/PlatformCompat.scala

@@ -30,7 +30,7 @@ object PlatformCompat {
       ec: ExecutionContext
   ): Future[T] = {
     val onComplete = Promise[T]()
-    val timeoutHandle = timers.setTimeout(duration.toMillis) {
+    val timeoutHandle = timers.setTimeout(duration.toMillis.toDouble) {
       onComplete.tryFailure(
         new TimeoutException(s"test timed out after $duration")
       )

munit/non-jvm/src/main/scala/munit/internal/junitinterface/JUnitEvent.scala

@@ -14,5 +14,5 @@ final class JUnitEvent(
     val throwable: OptionalThrowable = new OptionalThrowable,
     val duration: Long = -1L
 ) extends Event {
-  def fingerprint: Fingerprint = taskDef.fingerprint
+  def fingerprint(): Fingerprint = taskDef.fingerprint()
 }

munit/non-jvm/src/main/scala/munit/internal/junitinterface/JUnitReporter.scala

@@ -91,7 +91,7 @@ final class JUnitReporter(
       throwable: OptionalThrowable = new OptionalThrowable
   ): Unit = {
     val testName =
-      taskDef.fullyQualifiedName + "." +
+      taskDef.fullyQualifiedName() + "." +
         settings.decodeName(method)
     val selector = new TestSelector(testName)
     eventHandler.handle(
@@ -215,7 +215,7 @@ final class JUnitReporter(
 
   private def findTestFileName(trace: Array[StackTraceElement]): String =
     trace
-      .find(_.getClassName == taskDef.fullyQualifiedName)
+      .find(_.getClassName == taskDef.fullyQualifiedName())
       .map(_.getFileName)
       .orNull
 

munit/non-jvm/src/main/scala/munit/internal/junitinterface/JUnitRunner.scala

@@ -22,7 +22,7 @@ final class JUnitRunner(
   def done(): String = ""
 
   def serializeTask(task: Task, serializer: TaskDef => String): String =
-    serializer(task.taskDef)
+    serializer(task.taskDef())
 
   def deserializeTask(task: String, deserializer: String => TaskDef): Task =
     new JUnitTask(deserializer(task), runSettings, classLoader)

munit/non-jvm/src/main/scala/munit/internal/junitinterface/JUnitTask.scala

@@ -21,7 +21,7 @@ final class JUnitTask(
     classLoader: ClassLoader
 ) extends Task {
 
-  def tags: Array[String] = Array.empty
+  def tags(): Array[String] = Array.empty
 
   def execute(
       eventHandler: EventHandler,

munit/shared/src/main/scala-2.13/munit/internal/Compat.scala

@@ -1,5 +1,7 @@
 package munit.internal
 
+import language.reflectiveCalls
+
 object Compat {
   type LazyList[+T] = scala.LazyList[T]
   val LazyList = scala.LazyList

munit/shared/src/main/scala-2/munit/internal/MacroCompat.scala

@@ -2,6 +2,7 @@ package munit.internal
 
 import munit.Clue
 import munit.Location
+import scala.language.implicitConversions
 import scala.language.experimental.macros
 import scala.reflect.macros.blackbox.Context
 

munit/shared/src/main/scala/munit/Assertions.scala

@@ -118,7 +118,7 @@ trait Assertions extends MacroCompat.CompileErrorMacro {
       if (obtained != expected) {
 
         (obtained, expected) match {
-          case (a: Array[_], b: Array[_]) if a.sameElements(b) =>
+          case (a: Array[_], b: Array[_]) if a.sameElements[Any](b) =>
             // Special-case error message when comparing arrays. See
             // https://github.com/scalameta/munit/pull/393 and
             // https://github.com/scalameta/munit/issues/339 for a related

munit/shared/src/main/scala/munit/MUnitRunner.scala

@@ -33,7 +33,7 @@ class MUnitRunner(val cls: Class[_ <: Suite], newInstance: () => Suite)
     with Configurable {
 
   def this(cls: Class[_ <: Suite]) =
-    this(MUnitRunner.ensureEligibleConstructor(cls), () => cls.newInstance())
+    this(MUnitRunner.ensureEligibleConstructor(cls), () => cls.getDeclaredConstructor().newInstance())
 
   val suite: Suite = newInstance()
 
@@ -90,7 +90,7 @@ class MUnitRunner(val cls: Class[_ <: Suite], newInstance: () => Suite)
         val desc = Description.createTestDescription(
           cls,
           testName,
-          test.annotations: _*
+          test.annotations.toIndexedSeq: _*
         )
         desc
       }
@@ -243,7 +243,6 @@ class MUnitRunner(val cls: Class[_ <: Suite], newInstance: () => Suite)
       test: Test
   ): Future[BeforeAllResult] = {
     val context = new BeforeEach(test)
-    val fixtures = mutable.ListBuffer.empty[AnyFixture[_]]
     sequenceFutures(
       munitFixtures.iterator.map(f =>
         valueTransform(() => f.beforeEach(context)).map(_ => f)
@@ -369,7 +368,7 @@ class MUnitRunner(val cls: Class[_ <: Suite], newInstance: () => Suite)
   private def foreachUnsafe(
       thunks: Iterable[() => Any]
   ): ForeachUnsafeResult = {
-    var errors = mutable.ListBuffer.empty[Throwable]
+    val errors = mutable.ListBuffer.empty[Throwable]
     val async = mutable.ListBuffer.empty[Future[Any]]
     thunks.foreach { thunk =>
       try {

munit/shared/src/main/scala/munit/TestOptions.scala

@@ -46,6 +46,8 @@ object TestOptions extends TestOptionsConversions {
 
 trait TestOptionsConversions {
 
+  import language.implicitConversions
+
   /**
    * Implicitly create a TestOptions given a test name.
    * This allows writing `test("name") { ... }` even if `test` accepts a `TestOptions`

munit/shared/src/main/scala/munit/internal/difflib/Diffs.scala

@@ -7,7 +7,7 @@ object Diffs {
   def create(obtained: String, expected: String): Diff =
     new Diff(obtained, expected)
 
-  @deprecated("")
+  @deprecated("", since="")
   def assertNoDiff(
       obtained: String,
       expected: String,

munit/shared/src/main/scala/munit/internal/difflib/Equalizer.scala

@@ -6,7 +6,7 @@ trait Equalizer[T] {
 object Equalizer {
   def default[T]: Equalizer[T] = new Equalizer[T] {
     override def equals(original: T, revised: T): Boolean = {
-      original.equals(revised)
+      original == revised   //original.equals(revised)
     }
   }
 }

tests/jvm/src/test/scala/munit/AsyncFunFixtureOrderSuite.scala

@@ -4,7 +4,7 @@ import scala.concurrent.Future
 import scala.concurrent.Promise
 
 class AsyncFunFixtureOrderSuite extends FunSuite {
-  val latch: Promise[Unit] = Promise[Unit]
+  val latch: Promise[Unit] = Promise[Unit]()
   var completedFromTest: Option[Boolean] = None
   var completedFromTeardown: Option[Boolean] = None
 

tests/shared/src/main/scala/munit/ScalaCheckExceptionFrameworkSuite.scala

@@ -52,12 +52,12 @@ class ScalaCheckExceptionFrameworkSuites
       tags = Set(OnlyJVM),
       onEvent = { event =>
         if (
-          event.throwable.isDefined &&
-          event.throwable().get.getCause() != null
+          event.throwable().isDefined() &&
+          event.throwable().get().getCause() != null
         ) {
           event
             .throwable()
-            .get
+            .get()
             .getCause
             .getStackTrace()
             .take(2)

tests/shared/src/test/scala/munit/ComparisonFailExceptionSuite.scala

@@ -20,11 +20,11 @@ class ComparisonFailExceptionSuite extends BaseSuite {
     // console still uses `munitPrint()`, which would have displayed `List("1",
     // "2", "3")` instead of `List(1, 2, 3)`.
     assertNoDiff(
-      e.getActual,
+      e.getActual(),
       "List(1, 2, 3)"
     )
     assertNoDiff(
-      e.getExpected,
+      e.getExpected(),
       "List(1, 2)"
     )
     assertEquals(e.expected, List(1, 2))