Remove unused files and document root.scala

Author: odersky

compiler/src/dotty/tools/dotc/cc/CaptureAnnotation.scala

@@ -42,7 +42,7 @@ case class CaptureAnnotation(refs: CaptureSet, boxed: Boolean)(cls: Symbol) exte
       case cr: TermRef => ref(cr)
       case cr: TermParamRef => untpd.Ident(cr.paramName).withType(cr)
       case cr: ThisType => This(cr.cls)
-      case root(_) => ref(defn.captureRoot.termRef)
+      case root(_) => ref(root.cap)
       // TODO: Will crash if the type is an annotated type, for example `cap.rd`
     }
     val arg = repeated(elems, TypeTree(defn.AnyType))

compiler/src/dotty/tools/dotc/cc/CaptureOps.scala

@@ -218,7 +218,7 @@ extension (tree: Tree)
       elems
     case _ =>
       if tree.symbol.maybeOwner == defn.RetainsCapAnnot
-      then ref(defn.captureRoot.termRef) :: Nil
+      then ref(root.cap) :: Nil
       else Nil
 
 extension (tp: Type)

compiler/src/dotty/tools/dotc/cc/CaptureSet.scala

@@ -408,14 +408,20 @@ object CaptureSet:
 
   /** The universal capture set `{cap}` */
   def universal(using Context): CaptureSet =
-    defn.captureRoot.termRef.singletonCaptureSet
+    root.cap.singletonCaptureSet
+
+  /** The same as CaptureSet.universal but generated implicitly for
+   * references of Capability subtypes
+   */
+  def universalImpliedByCapability(using Context) =
+    defn.universalCSImpliedByCapability
 
   def fresh(owner: Symbol = NoSymbol)(using Context): CaptureSet =
     root.Fresh.withOwner(owner).singletonCaptureSet
 
   /** The shared capture set `{cap.rd}` */
   def shared(using Context): CaptureSet =
-    defn.captureRoot.termRef.readOnly.singletonCaptureSet
+    root.cap.readOnly.singletonCaptureSet
 
   /** Used as a recursion brake */
   @sharable private[dotc] val Pending = Const(SimpleIdentitySet.empty)

compiler/src/dotty/tools/dotc/cc/Existential.scala

@@ -373,7 +373,7 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
        */
       def stripImpliedCaptureSet(tp: Type): Type = tp match
         case tp @ CapturingType(parent, refs)
-        if (refs eq defn.universalCSImpliedByCapability) && !tp.isBoxedCapturing =>
+        if (refs eq CaptureSet.universalImpliedByCapability) && !tp.isBoxedCapturing =>
           parent
         case _ => tp
 
@@ -401,7 +401,7 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
           && !t.isSingleton
           && (!sym.isConstructor || (t ne tp.finalResultType))
             // Don't add ^ to result types of class constructors deriving from Capability
-        then CapturingType(t, defn.universalCSImpliedByCapability, boxed = false)
+        then CapturingType(t, CaptureSet.universalImpliedByCapability, boxed = false)
         else normalizeCaptures(mapFollowingAliases(t))
 
       def innerApply(t: Type) =

compiler/src/dotty/tools/dotc/cc/Fresh.scala

@@ -132,7 +132,7 @@ object Synthetics:
       val (pt: PolyType) = info: @unchecked
       val (mt: MethodType) = pt.resType: @unchecked
       val (enclThis: ThisType) = owner.thisType: @unchecked
-      val paramCaptures = CaptureSet(enclThis, defn.captureRoot.termRef)
+      val paramCaptures = CaptureSet(enclThis, root.cap)
       pt.derivedLambdaType(resType = MethodType(mt.paramNames)(
         mt1 => mt.paramInfos.map(_.capturing(paramCaptures)),
         mt1 => CapturingType(mt.resType, CaptureSet(enclThis, mt1.paramRefs.head))))
@@ -150,7 +150,7 @@ object Synthetics:
     def transformCompareCaptures =
       val (enclThis: ThisType) = symd.owner.thisType: @unchecked
       MethodType(
-        defn.ObjectType.capturing(CaptureSet(defn.captureRoot.termRef, enclThis)) :: Nil,
+        defn.ObjectType.capturing(CaptureSet(root.cap, enclThis)) :: Nil,
         defn.BooleanType)
 
     symd.copySymDenotation(info = symd.name match