Simplify Annotation API for type mapping

Keep only mapWith

Author: odersky

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

@@ -47,11 +47,6 @@ object Annotations {
     /** The tree evaluation has finished. */
     def isEvaluated: Boolean = true
 
-    /** The annotation should be part of mappings?
-     *  Currently overridden only in ConcreteAnnotation, which simulates the previous behavior.
-     */
-    def isMappable: Boolean = false
-
     /** Normally, map type map over all tree nodes of this annotation, but can
      *  be overridden. Returns EmptyAnnotation if type type map produces a range
      *  type, since ranges cannot be types of trees.
@@ -83,7 +78,6 @@ object Annotations {
 
   case class ConcreteAnnotation(t: Tree) extends Annotation {
     def tree(using Context): Tree = t
-    override def isMappable = true
     override def argsText(printer: Printer): Text =
       def toTextArg(arg: Tree): Text = arg match
         case Typed(SeqLiteral(elems, _), _) => printer.toTextGlobal(elems, ", ")
@@ -143,6 +137,7 @@ object Annotations {
       if (tree eq this.tree) this else ConcreteBodyAnnotation(tree)
     override def arguments(using Context): List[Tree] = Nil
     override def ensureCompleted(using Context): Unit = ()
+    override def mapWith(tm: TypeMap)(using Context) = this
   }
 
   class ConcreteBodyAnnotation(body: Tree) extends BodyAnnotation {

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

@@ -5439,10 +5439,7 @@ object Types {
 
         case tp @ AnnotatedType(underlying, annot) =>
           val underlying1 = this(underlying)
-          val annot1 =
-            if (underlying1 ne underlying) || annot.isMappable
-            then annot.mapWith(this)
-            else annot
+          val annot1 = annot.mapWith(this)
           if annot1 eq EmptyAnnotation then underlying1
           else derivedAnnotatedType(tp, underlying1, annot1)