Use IFT for Annotation.Child creation

Author: odersky

compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -966,7 +966,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       val sym = tree.symbol
       if (sym.is(Method)) {
         val setter = sym.setter.orElse {
-          assert(sym.name.isSetterName && sym.info.firstParamTypes.nonEmpty)
+          assert(sym.name.isSetterName && sym.info.firstParamTypes.nonEmpty, sym)
           sym
         }
         val qual = tree match {

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

@@ -75,6 +75,7 @@ object Annotations {
   }
 
   case class LazyBodyAnnotation(private var bodyExpr: Context => Tree) extends BodyAnnotation {
+    // TODO: Make `bodyExpr` an IFT once #6865 os in bootstrap
     private[this] var evaluated = false
     private[this] var myBody: Tree = _
     def tree(implicit ctx: Context): Tree = {
@@ -159,17 +160,17 @@ object Annotations {
     object Child {
 
       /** A deferred annotation to the result of a given child computation */
-      def apply(delayedSym: Context => Symbol, span: Span)(implicit ctx: Context): Annotation = {
+      def later(delayedSym: given Context => Symbol, span: Span)(implicit ctx: Context): Annotation = {
         def makeChildLater(implicit ctx: Context) = {
-          val sym = delayedSym(ctx)
+          val sym = delayedSym
           New(defn.ChildAnnotType.appliedTo(sym.owner.thisType.select(sym.name, sym)), Nil)
             .withSpan(span)
         }
         deferred(defn.ChildAnnot)(makeChildLater(ctx))
       }
 
       /** A regular, non-deferred Child annotation */
-      def apply(sym: Symbol, span: Span)(implicit ctx: Context): Annotation = apply(_ => sym, span)
+      def apply(sym: Symbol, span: Span)(implicit ctx: Context): Annotation = later(given _ => sym, span)
 
       def unapply(ann: Annotation)(implicit ctx: Context): Option[Symbol] =
         if (ann.symbol == defn.ChildAnnot) {

compiler/src/dotty/tools/dotc/core/unpickleScala2/Scala2Unpickler.scala

@@ -849,8 +849,7 @@ class Scala2Unpickler(bytes: Array[Byte], classRoot: ClassDenotation, moduleClas
       val start = readIndex
       readNat() // skip reference for now
       target.addAnnotation(
-          Annotation.Child(implicit ctx =>
-              atReadPos(start, () => readSymbolRef()), NoSpan))
+          Annotation.Child.later(atReadPos(start, () => readSymbolRef()), NoSpan))
     }
   }