Implicit parameters should warn at call site in >= 3.7

[hamzaremmal]

Closes #22440

TODO:

• Add test with -Wconf
• Handle desugaring to generate valid code:

  abstract class Base(implicit config: Int)
  case class A(x: Int)(implicit config: Int) extends Base

should not be desugared to (anymore):

abstract class Base(implicit config: Int) extends Object() {
      private[this] implicit val config: Int
    }
    case class A(x: Int)(implicit config: Int) extends Test.Base()(config),
      _root_.scala.Product, _root_.scala.Serializable {
      val x: Int
      private[this] implicit val config: Int
      def copy(x: Int)(implicit config: Int): Test.A = new Test.A(x)(config)
      def copy$default$1: Int @uncheckedVariance = A.this.x
      def _1: Int = this.x
    }
    final lazy module val A: Test.A = new Test.A()
    final module class A() extends AnyRef() { this: Test.A.type =>
      def apply(x: Int)(implicit config: Int): Test.A = new Test.A(x)(config)
      def unapply(x$1: Test.A): Test.A = x$1
      override def toString: String = "A"
    }

but rather:

abstract class Base(implicit config: Int) extends Object() {
      private[this] implicit val config: Int
    }
    case class A(x: Int)(implicit config: Int) extends Test.Base()(using config),
      _root_.scala.Product, _root_.scala.Serializable {
      val x: Int
      private[this] implicit val config: Int
      def copy(x: Int)(implicit config: Int): Test.A = new Test.A(x)(using config)
      def copy$default$1: Int @uncheckedVariance = A.this.x
      def _1: Int = this.x
    }
    final lazy module val A: Test.A = new Test.A()
    final module class A() extends AnyRef() { this: Test.A.type =>
      def apply(x: Int)(implicit config: Int): Test.A = new Test.A(x)(using config)
      def unapply(x$1: Test.A): Test.A = x$1
      override def toString: String = "A"
    }

[tgodzik]

Thanks!

[xuwei-k]

• 🤔 confusing Implicit parameters should be provided with a using clause message if implicit default param #22567