Exclusive capabilities

compiler/src/dotty/tools/backend/jvm/BTypesFromSymbols.scala

@@ -285,7 +285,7 @@ class BTypesFromSymbols[I <: DottyBackendInterface](val int: I, val frontendAcce
     // tests/run/serialize.scala and https://github.com/typelevel/cats-effect/pull/2360).
     val privateFlag = !sym.isClass && (sym.is(Private) || (sym.isPrimaryConstructor && sym.owner.isTopLevelModuleClass))
 
-    val finalFlag = sym.is(Final) && !toDenot(sym).isClassConstructor && !sym.is(Mutable, butNot = Accessor) && !sym.enclosingClass.is(Trait)
+    val finalFlag = sym.is(Final) && !toDenot(sym).isClassConstructor && !sym.isMutableVar && !sym.enclosingClass.is(Trait)
 
     import asm.Opcodes.*
     import GenBCodeOps.addFlagIf

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

@@ -2231,6 +2231,8 @@ object desugar {
               New(ref(defn.RepeatedAnnot.typeRef), Nil :: Nil))
         else if op.name == nme.CC_REACH then
           Apply(ref(defn.Caps_reachCapability), t :: Nil)
+        else if op.name == nme.CC_READONLY then
+          Apply(ref(defn.Caps_readOnlyCapability), t :: Nil)
         else
           assert(ctx.mode.isExpr || ctx.reporter.errorsReported || ctx.mode.is(Mode.Interactive), ctx.mode)
           Select(t, op.name)

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

@@ -755,7 +755,7 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
    */
   def isVariableOrGetter(tree: Tree)(using Context): Boolean = {
     def sym = tree.symbol
-    def isVar = sym.is(Mutable)
+    def isVar = sym.isMutableVarOrAccessor
     def isGetter =
       mayBeVarGetter(sym) && sym.owner.info.member(sym.name.asTermName.setterName).exists
 

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

@@ -206,6 +206,8 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
 
     case class Var()(implicit @constructorOnly src: SourceFile) extends Mod(Flags.Mutable)
 
+    case class Mut()(implicit @constructorOnly src: SourceFile) extends Mod(Flags.Mutable)
+
     case class Implicit()(implicit @constructorOnly src: SourceFile) extends Mod(Flags.Implicit)
 
     case class Given()(implicit @constructorOnly src: SourceFile) extends Mod(Flags.Given)
@@ -332,6 +334,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
 
     def isEnumCase: Boolean = isEnum && is(Case)
     def isEnumClass: Boolean = isEnum && !is(Case)
+    def isMutableVar: Boolean = is(Mutable) && mods.exists(_.isInstanceOf[Mod.Var])
   }
 
   @sharable val EmptyModifiers: Modifiers = Modifiers()

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

@@ -55,11 +55,6 @@ case class CaptureAnnotation(refs: CaptureSet, boxed: Boolean)(cls: Symbol) exte
     if (this.refs eq refs) && (this.boxed == boxed) then this
     else CaptureAnnotation(refs, boxed)(cls)
 
-  override def sameAnnotation(that: Annotation)(using Context): Boolean = that match
-    case CaptureAnnotation(refs, boxed) =>
-      this.refs == refs && this.boxed == boxed && this.symbol == that.symbol
-    case _ => false
-
   override def mapWith(tm: TypeMap)(using Context) =
     val elems = refs.elems.toList
     val elems1 = elems.mapConserve(tm)