Consider annotations when computing method type dependency information

Author: odersky

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

@@ -3579,6 +3579,14 @@ object Types {
     private var myDependencyStatus: DependencyStatus = Unknown
     private var myParamDependencyStatus: DependencyStatus = Unknown
 
+    private def refersToParam(tree: Tree)(using Context): Boolean =
+      tree.existsSubTree {
+        case id: Ident => id.tpe match
+          case TermParamRef(`thisLambdaType`, _) => true
+          case _ => false
+        case _ => false
+      }
+
     private def depStatus(initial: DependencyStatus, tp: Type)(using Context): DependencyStatus =
       class DepAcc extends TypeAccumulator[DependencyStatus]:
         def apply(status: DependencyStatus, tp: Type) = compute(status, tp, this)
@@ -3604,6 +3612,8 @@ object Types {
           case tp: AppliedType => tp.fold(status, compute(_, _, theAcc))
           case tp: TypeVar if !tp.isInstantiated => combine(status, Provisional)
           case tp: TermParamRef if tp.binder eq thisLambdaType => TrueDeps
+          case AnnotatedType(parent, ConcreteAnnotation(ann)) =>
+            if refersToParam(ann) then TrueDeps else compute(status, parent, theAcc)
           case _: ThisType | _: BoundType | NoPrefix => status
           case _ =>
             (if theAcc != null then theAcc else DepAcc()).foldOver(status, tp)
@@ -3656,8 +3666,10 @@ object Types {
       if (isResultDependent) {
         val dropDependencies = new ApproximatingTypeMap {
           def apply(tp: Type) = tp match {
-            case tp @ TermParamRef(thisLambdaType, _) =>
+            case tp @ TermParamRef(`thisLambdaType`, _) =>
               range(defn.NothingType, atVariance(1)(apply(tp.underlying)))
+            case AnnotatedType(parent, ConcreteAnnotation(ann)) if refersToParam(ann) =>
+              mapOver(parent)
             case _ => mapOver(tp)
           }
         }