chore: deprecate scala.annotation.transparentTrait

Author: hamzaremmal

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -1048,7 +1048,6 @@ class Definitions {
   @tu lazy val NowarnAnnot: ClassSymbol = requiredClass("scala.annotation.nowarn")
   @tu lazy val UnusedAnnot: ClassSymbol = requiredClass("scala.annotation.unused")
   @tu lazy val UnrollAnnot: ClassSymbol = requiredClass("scala.annotation.unroll")
-  @tu lazy val TransparentTraitAnnot: ClassSymbol = requiredClass("scala.annotation.transparentTrait")
   @tu lazy val NativeAnnot: ClassSymbol = requiredClass("scala.native")
   @tu lazy val RepeatedAnnot: ClassSymbol = requiredClass("scala.annotation.internal.Repeated")
   @tu lazy val RuntimeCheckedAnnot: ClassSymbol = requiredClass("scala.annotation.internal.RuntimeChecked")

compiler/src/dotty/tools/dotc/core/SymDenotations.scala

@@ -1220,9 +1220,7 @@ object SymDenotations {
       || accessBoundary(defn.RootClass).isProperlyContainedIn(symbol.topLevelClass)
 
     final def isTransparentClass(using Context): Boolean =
-      is(TransparentType)
-      || defn.isAssumedTransparent(symbol)
-      || isClass && hasAnnotation(defn.TransparentTraitAnnot)
+      is(TransparentType) || defn.isAssumedTransparent(symbol)
 
     /** The class containing this denotation which has the given effective name. */
     final def enclosingClassNamed(name: Name)(using Context): Symbol = {

library/src/scala/annotation/transparentTrait.scala

@@ -5,4 +5,5 @@ package scala.annotation
  *  are not inferred when combined with other types in an intersection.
  *  See reference/other-new-features/transparent-traits.html for details.
  */
+@deprecated(message = "Transparent traits/classes via annotations is no longer supported. Use instead the `transparent` modifier", since = "3.8.0")
 final class transparentTrait extends StaticAnnotation