Fixed many compiler warnings after Scala 3.4 migration

Author: yadavan88

scala-core-collections-modules/scala-core-collections-3/src/main/scala/com/baeldung/scala/commoncollections/ScalaCollections.scala

@@ -10,7 +10,7 @@ object ScalaCollections {
 
   val numbersListWithOperator: List[Int] = 1 :: 2 :: 3 :: 4 :: Nil
   val emptyListWithNil: List[Int] = Nil
-  val x :: xs = numbersList
+  val x :: xs = numbersList: @unchecked
 
   // Scala Set
   val emptySet: Set[Int] = Set()

scala-core-modules/scala-core-2/src/main/scala/com/baeldung/scala/forcomprehension/ForComprehension.scala

@@ -56,7 +56,7 @@ object ForComprehension {
     def foreach(f: A => Unit): Unit = f(result)
     def map[B](f: A => B): Result[B] = Result(f(result))
     def flatMap[B](f: A => Result[B]): Result[B] = f(result)
-    def withFilter(f: A => Boolean): Result[_] =
+    def withFilter(f: A => Boolean): Result[?] =
       if (f(result)) this else EmptyResult
   }
 

scala-core-modules/scala-core-2/src/main/scala/com/baeldung/scala/underscore/UnderscoreUsages.scala

@@ -2,7 +2,7 @@ package com.baeldung.scala.underscore
 
 object UnderscoreUsages {
 
-  def getLength(x: List[List[_]]): Int = x.length
+  def getLength(x: List[List[?]]): Int = x.length
 
   def itemTransaction(price: Double): String = {
     price match {
@@ -33,7 +33,7 @@ object UnderscoreUsages {
     }
   }
 
-  def list_++(list: List[_]): List[_] = List.concat(list, list)
+  def list_++(list: List[?]): List[?] = List.concat(list, list)
 
   trait ObjectContainer[T[_]] { // higher kinded type parameter
     def checkIfEmpty[A](collection: T[A]): Boolean

scala-core-modules/scala-core-2/src/test/scala/com/baeldung/scala/underscore/UnderscoreUsagesUnitTest.scala

@@ -48,7 +48,7 @@ class UnderscoreUsagesUnitTest extends AnyWordSpec with Matchers {
       b shouldBe "b"
 
       text = "a,b,c,d,e"
-      val Array(a2, _*) = text.split(",")
+      val Array(a2, _*) = text.split(","): @unchecked
       a2 shouldBe "a"
 
       val Array(a3, b3, _, d, e) = text.split(",")
@@ -58,20 +58,20 @@ class UnderscoreUsagesUnitTest extends AnyWordSpec with Matchers {
       e shouldBe "e"
     }
     "work in reassigning a a function to a value" in {
-      val times = multiplier _
+      val times = multiplier
       multiplier(8, 13) shouldBe times(8, 13)
     }
     "work in converting a sequence to variable arguments" in {
       val sumable = Seq(4, 5, 10, 3)
-      val sumOfSumable = sum(sumable: _*)
+      val sumOfSumable = sum(sumable*)
       sumOfSumable shouldBe 22
     }
     "generate a partially applied function" in {
       val sumToTen = sum(10, _: Int)
       val sumFiveAndTen = sumToTen(5)
       sumFiveAndTen shouldBe 15
 
-      val foo = bar(1, 2) _
+      val foo = bar(1, 2)
       foo("Some string", "Another string")(3 / 5, 6 / 5) shouldBe 1
     }
     "work in overriding a method's setter" in {

scala-core-modules/scala-core-3/src/main/scala/com/baeldung/scala/accessmodifiers/Figure.scala

@@ -3,12 +3,12 @@ package com.baeldung.scala.accessmodifiers
 import java.util.UUID.randomUUID
 
 abstract class Figure {
-  private[this] val code =
+  private val code =
     randomUUID.toString // accessible in the scope of the object-only
   def printCode: Unit = println(s"$code") // public access
 
   protected[accessmodifiers] val color: String // accessible in the scope of the package
-  protected[this] val lineWidth: Int // accessible for instances of this class and its subclasses instances
+  protected val lineWidth: Int // accessible for instances of this class and its subclasses instances
 
   protected val topPoint: Double // accessible in the scope of the class and subclasses
   protected val rightMostPoint: Double

scala-core-modules/scala-core-3/src/main/scala/com/baeldung/scala/iteratorsvsstreamsvsviews/NonStrictDataStructures.scala

@@ -8,7 +8,7 @@ object NonStrictDataStructures {
   val stream = data.toStream
   // todo: check if this is ok, better to separate into separate module
   // val view: AnyRef with SeqView[Int, Seq[Int]] = data.view
-  val view: AnyRef with SeqView[Int] = data.view
+  val view: AnyRef & SeqView[Int] = data.view
 }
 
 case class Factorial() {

scala-core-modules/scala-core-3/src/main/scala/com/baeldung/scala/typecasts/TypeErasure.scala

@@ -13,6 +13,6 @@ object TypeErasure {
 
   // Simply function that converts a variable number of values to a List of that type
   def convertValuesToList[T](values: T*): List[T] = {
-    List[T](values: _*)
+    List[T](values*)
   }
 }

scala-core-modules/scala-core-3/src/test/scala/com/baeldung/scala/typecasts/TypeErasureUnitTest.scala

@@ -39,7 +39,7 @@ class TypeErasureUnitTest extends AnyWordSpec with Matchers {
     "work with varargs" in {
       def varargFn(str: String*) = str.length
       val input = Seq("Hello", "World")
-      assert(varargFn(input: _*) == 2)
+      assert(varargFn(input*) == 2)
     }
   }
 }

scala-core-modules/scala-core-6/src/main/scala/com/baeldung/scala/functions/Functions.scala

@@ -35,8 +35,8 @@ object Functions {
   // getNameLengthDef.andThen(multiplyByTwoDef) //doesn't compile
 
   /** Method to Function value */
-  val getNameLengthDefFnValue = getNameLengthDef _
-  val multiplyByTwoDefFnValue = multiplyByTwoDef _
+  val getNameLengthDefFnValue = getNameLengthDef
+  val multiplyByTwoDefFnValue = multiplyByTwoDef
 
   getNameLengthDefFnValue.andThen(multiplyByTwoDefFnValue) // compiles
 

scala-core-modules/scala-core-7/src/main/scala/com/baeldung/scala/productserializable/ColorInference.scala

@@ -14,7 +14,7 @@ object ColorV2 {
 
 object Inference {
   def isError: Boolean = true
-  val consoleColor: Product with Serializable with Color =
+  val consoleColor: Product & Serializable & Color =
     if (isError) Color.Red else Color.Green
 
   val consoleColorV2: Color = if (isError) Color.Red else Color.Green

scala-core-modules/scala-core-7/src/test/scala/com/baeldung/scala/arrays/CopyAnArrayToAnotherUnitTest.scala

@@ -7,7 +7,7 @@ class CopyAnArrayToAnotherUnitTest extends AnyFlatSpec with Matchers {
   val array1 = Array(1, 2, 3, 4)
 
   "splat operator" should "copy an entire array to another" in {
-    var array2 = Array(array1: _*)
+    var array2 = Array(array1*)
     array1(1) should be(array2(1))
     array1 should not be (array2)
 

scala-core-modules/scala-core-7/src/test/scala/com/baeldung/scala/arrays/InitializeAnArrayUnitTest.scala

@@ -30,7 +30,7 @@ class InitializeAnArrayUnitTest extends AnyFlatSpec with Matchers {
 
   "splat operator" should "copy an entire list to an array" in {
     var list = List(1, 2, 3, 4)
-    var array = Array[Int](list: _*)
+    var array = Array[Int](list*)
 
     array(1) should be(list(1))
     array.length should be(4)

scala-core-modules/scala-core-8/src/main/scala/com/baeldung/scala/braces/NoParenthesis.scala

@@ -9,6 +9,6 @@ object NoParenthesis extends App {
   // greet "Alice"
 
   // But this works and it equivalent to greet("Alice")
-  this greet "Alice"
+  this `greet` "Alice"
 
 }

scala-core-modules/scala-core-8/src/test/scala/com/baeldung/scala/reverselists/ListReverserUnitTest.scala

@@ -9,14 +9,14 @@ class ListReverserUnitTest extends AnyWordSpec with BeforeAndAfterEach {
 
   import ListReverser._
 
-  def testReverseSmallList(f: Seq[_] => Seq[_]): Assertion = {
+  def testReverseSmallList(f: Seq[?] => Seq[?]): Assertion = {
     val list = List(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
     val expectedReversedList = List(10, 9, 8, 7, 6, 5, 4, 3, 2, 1)
     val actualReversedList = f(list)
     assertResult(expectedReversedList)(actualReversedList)
   }
 
-  def testReverseBigList(f: Seq[_] => Seq[_]): Assertion = {
+  def testReverseBigList(f: Seq[?] => Seq[?]): Assertion = {
     val n = 100_000
     val vector: Vector[String] =
       (0 to n).foldLeft(Vector.empty[String])((v, _) =>
@@ -29,7 +29,7 @@ class ListReverserUnitTest extends AnyWordSpec with BeforeAndAfterEach {
   }
 
   "The naive list reverser" should {
-    val reversingFunction: Seq[_] => Seq[_] = naiveRecursiveReverse
+    val reversingFunction: Seq[?] => Seq[?] = naiveRecursiveReverse
 
     "reverse small lists" in {
       testReverseSmallList(reversingFunction)
@@ -41,7 +41,7 @@ class ListReverserUnitTest extends AnyWordSpec with BeforeAndAfterEach {
   }
 
   "The tail-recursive list reverser" should {
-    val reversingFunction: Seq[_] => Seq[_] = tailRecursiveReverse
+    val reversingFunction: Seq[?] => Seq[?] = tailRecursiveReverse
 
     "reverse small lists" in {
       testReverseSmallList(reversingFunction)
@@ -53,7 +53,7 @@ class ListReverserUnitTest extends AnyWordSpec with BeforeAndAfterEach {
   }
 
   "The folding list reverser" should {
-    val reversingFunction: Seq[_] => Seq[_] = foldBasedReverse
+    val reversingFunction: Seq[?] => Seq[?] = foldBasedReverse
 
     "reverse small lists" in {
       testReverseSmallList(reversingFunction)

scala-core-modules/scala-core-9/src/test/scala/com/baeldung/scala/classT/ClassTUnitTest.scala

@@ -19,7 +19,7 @@ class ClassTUnitTest extends AnyFlatSpec with Matchers {
         )
 
       // Instantiate the class with arguments
-      Some(constructor.newInstance(args: _*).asInstanceOf[T])
+      Some(constructor.newInstance(args*).asInstanceOf[T])
     } catch {
       case e: Exception =>
         println(s"Error creating instance of ${clazz.getName}: ${e.getMessage}")
@@ -37,7 +37,7 @@ class ClassTUnitTest extends AnyFlatSpec with Matchers {
 
   "createInstance with .getClass" should "successfully create another instance of Person" in {
     val dummyPerson = new Person("Dummy")
-    val personClass: Class[_ <: Person] = dummyPerson.getClass
+    val personClass: Class[? <: Person] = dummyPerson.getClass
     val personInstance = createInstance(personClass, Array("Jane Doe": AnyRef))
 
     personInstance should not be empty
@@ -46,7 +46,7 @@ class ClassTUnitTest extends AnyFlatSpec with Matchers {
 
   "createInstance with .getClass" should "use the type of the variable to bound the type" in {
     val dummyPerson: Object = new Person("Dummy")
-    val personClass: Class[_ <: AnyRef] = dummyPerson.getClass
+    val personClass: Class[? <: AnyRef] = dummyPerson.getClass
     val personInstance = createInstance(personClass, Array("Jane Doe": AnyRef))
 
     personInstance should not be empty

scala-core-modules/scala-core-9/src/test/scala/com/baeldung/scala/destructuring/DestructuringUnitTest.scala

@@ -28,12 +28,12 @@ class DestructuringUnitTest extends AnyFlatSpec with Matchers {
         // Reassemble and call the specific handler
         processEmail(
           Email(subject, body, recipient)
-        ).msg startsWith ("Sent email to ")
+        ).msg `startsWith` ("Sent email to ")
 
       case SMS(number, message) =>
         println(s"Logging SMS to $number: $message")
         // Reassemble and call the specific handler
-        processSMS(SMS(number, message)).msg startsWith ("Sending SMS to")
+        processSMS(SMS(number, message)).msg `startsWith` ("Sending SMS to")
     }
   }
 
@@ -46,46 +46,46 @@ class DestructuringUnitTest extends AnyFlatSpec with Matchers {
         // Reassemble and call the specific handler
         processEmail(
           email
-        ).msg startsWith ("Sent email to ")
+        ).msg `startsWith` ("Sent email to ")
 
       case sms: SMS =>
         println(s"Logging SMS to ${sms.number}: ${sms.message}")
         // Reassemble and call the specific handler
-        processSMS(sms).msg startsWith ("Sending SMS to")
+        processSMS(sms).msg `startsWith` ("Sending SMS to")
     }
   }
 
   "We" should "be able to pattern match with @" in {
     getRandomElement(notifications, random) match {
       case email @ Email(subject, _, recipient) =>
         println(s"Logging Email to $recipient with subject $subject")
-        processEmail(email).msg startsWith ("Sent email to ")
+        processEmail(email).msg `startsWith` ("Sent email to ")
 
       case sms @ SMS(number, message) =>
         println(s"Logging SMS to $number: $message")
         // Reassemble and call the specific handler
-        processSMS(sms).msg startsWith ("Sending SMS to")
+        processSMS(sms).msg `startsWith` ("Sending SMS to")
     }
   }
 
   "We" should "be able to use @ while declaring a variable" in {
     val email @ Email(subject, _, recipient) = getRandomElement(emails, random)
     println(s"Logging Email to $recipient with subject $subject")
-    processEmail(email).msg startsWith ("Sent email to ")
+    processEmail(email).msg `startsWith` ("Sent email to ")
   }
 
   "We" should "be able to use @ in for comprehensions" in {
     for (email @ Email(subject, _, recipient) <- emails) {
       println(s"Logging Email to $recipient with subject $subject")
-      processEmail(email).msg startsWith ("Sent email to ")
+      processEmail(email).msg `startsWith` ("Sent email to ")
     }
   }
 
   "We" should "be able to use @ in a subpattern" in {
     emails match {
       case _ :: (email2 @ Email(subject, _, recipient)) :: _ =>
         println(s"Logging 2nd Email to $recipient with subject $subject")
-        processEmail(email2).msg startsWith ("Sent email to ")
+        processEmail(email2).msg `startsWith` ("Sent email to ")
 
       case _ =>
         println(s"Only one message")

scala-core-modules/scala-core-fp/src/test/scala/com/baeldung/scala/currying/CurryingUnitTest.scala

@@ -20,7 +20,7 @@ class CurryingUnitTest extends Matchers {
     : Unit = {
     def sum(x: Int, y: Int): Int = x + y
 
-    val curriedSum: Int => Int => Int = (sum _).curried
+    val curriedSum: Int => Int => Int = (sum).curried
 
     sum(1, 2) shouldBe 3
     curriedSum(1)(2) shouldBe 3

scala-core-modules/scala-core-oop/src/main/scala/com/baeldung/scala/generics/GenericsIntro.scala

@@ -69,7 +69,7 @@ object GenericsIntro {
   }
 
   object NonGenericMethods {
-    def totalSize(list1: List[_], list2: List[_]): Int =
+    def totalSize(list1: List[?], list2: List[?]): Int =
       list1.length + list2.length
     def run() = {
       val rabbits = List[Rabbit](Rabbit(2), Rabbit(3), Rabbit(7))

scala-core-modules/scala-core-oop/src/main/scala/com/baeldung/scala/lifting/Examples.scala

@@ -31,8 +31,8 @@ object Examples {
   def add5(x: Int) = x + 5
   def isEven(x: Int) = x % 2 == 0
 
-  val funcAdd5 = add5 _
-  val funcIsEven = isEven _
+  val funcAdd5 = add5
+  val funcIsEven = isEven
 
   val sayHello: Future[Option[String]] = Future.successful(Some("Say hello to"))
   val firstname: Future[String] = Future.successful("Fabio")

scala-core-modules/scala-core/src/test/scala/com/baeldung/scala/higherorder/HigherOrderFunctionsUnitTest.scala

@@ -40,7 +40,7 @@ class HigherOrderFunctionsUnitTest {
 
     // partial application of curried function
     // trailing underscore is required to make function type explicit
-    val sumMod5 = sum(mod(5)) _
+    val sumMod5 = sum(mod(5))
 
     assertEquals(10, sumMod5(6, 10))
   }

scala-design-patterns/src/main/scala/com/baeldung/scala/cakepattern/CakePattern.scala

@@ -36,7 +36,7 @@ object CakePattern {
   }
 
   trait TestExecutorComponentWithLogging {
-    this: TestEnvironmentComponent with LoggingComponent =>
+    this: TestEnvironmentComponent & LoggingComponent =>
     val testExecutor: TestExecutor
     class TestExecutor {
       def execute(tests: List[Test]): Boolean = {

scala-lang-modules/scala-lang-2/src/test/scala/com/baeldung/scala/voidtypes/NullTypeAndNullValueUnitTest.scala

@@ -13,7 +13,7 @@ class NullTypeAndNullValueUnitTest extends AnyFunSuite {
 
   test("null equality check using equals ") {
     val exceptionThrown = intercept[NullPointerException] {
-      NullTypeAndnullValue.nullValue equals NullTypeAndnullValue.nullRefCar
+      NullTypeAndnullValue.nullValue `equals` NullTypeAndnullValue.nullRefCar
     }
   }
 

scala-lang-modules/scala-lang-2/src/test/scala/com/baeldung/scala/withtrait/WithTraitUnitTest.scala

@@ -51,28 +51,28 @@ object WithTraitSpec {
   val pat: Person =
     new Person("Pat", "123 Main St.", LocalDate.of(1933, 10, 11))
 
-  val mary: Person with Musician =
+  val mary: Person & Musician =
     new Person("Mary", "456 Second St.", LocalDate.of(1982, 9, 9))
       with Musician {
       override val instrument: String = "guitar"
     }
 
-  val prudence: Person with Politician =
+  val prudence: Person & Politician =
     new Person("Prudence", "789 Third St.", LocalDate.of(1972, 6, 3))
       with Politician
 
-  val giorgio: Person with Politician with Musician =
+  val giorgio: Person & Politician & Musician =
     new Person("Giorgio", "121 Fourth St.", LocalDate.of(1980, 2, 19))
       with Politician
       with Musician {
       override val instrument: String = "flute"
     }
 
-  val ellie: Animal with Musician =
+  val ellie: Animal & Musician =
     new Animal("Ellie", "elephant") with Musician {
       override val instrument: String = "trombone"
     }
 
-  val vasily: Animal with Politician =
+  val vasily: Animal & Politician =
     new Animal("Vasily", "monkey") with Politician
 }

scala-lang-modules/scala-lang/src/main/scala/com/baeldung/scala/operators/ScalaOperators.scala

@@ -9,11 +9,11 @@ object ScalaOperators {
   assert(1.+(2) == 3)
 
   assert("Baeldung".charAt(0) == 'B')
-  val char: Char = "Baeldung" charAt 0
+  val char: Char = "Baeldung" `charAt` 0
   assert(char == 'B')
 
   assert("Baeldung".replace('g', 'G') == "BaeldunG")
-  val str: String = "Baeldung" replace ('g', 'G')
+  val str: String = "Baeldung" `replace` ('g', 'G')
   assert(str == "BaeldunG")
 
   // Unary operator notation