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