Don't add another refinement for tracked class parameters

Author: odersky

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

@@ -645,6 +645,9 @@ extension (cls: ClassSymbol) {
           case TypeRef(prefix: ThisType, _) if prefix.cls == cls => locals
           case TypeRef(prefix, _) => locals.map(AsSeenFromMap(prefix, cls.owner))
           case _ => locals
+
+  def refiningGetterNamed(name: Name)(using Context): Symbol =
+    cls.info.decls.lookup(name).suchThat(_.isRefiningParamAccessor).symbol
 }
 
 extension (sym: Symbol) {

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

@@ -983,9 +983,10 @@ class CheckCaptures extends Recheck, SymTransformer:
         var refined: Type = core
         var allCaptures: CaptureSet = initCs ++ cls.capturesImpliedByFields(core).refs
         for (getterName, argType) <- mt.paramNames.lazyZip(argTypes) do
-          val getter = cls.info.member(getterName).suchThat(_.isRefiningParamAccessor).symbol
+          val getter = cls.refiningGetterNamed(getterName)
           if !getter.is(Private) && getter.hasTrackedParts then
-            refined = refined.refinedOverride(getterName, argType.unboxed)
+            if !getter.is(Tracked) then
+              refined = refined.refinedOverride(getterName, argType.unboxed)
               // We can assume unboxed since the use set contributed by field selection is also the capture set
               // So unboxing will not add anything to the use sets.
               // This trick is also the principal reason why we can't make refineConstructorInstance