SymDenotation.isEffectivelyFinal

Helper method that tests weather this particular
SymDenotation cant have overrides: eg if it's defined in module class,
if it is inner method, if it is method of anonymous class, etc.

Author: DarkDimius

src/dotty/tools/dotc/core/Flags.scala

@@ -470,6 +470,15 @@ object Flags {
   /** Labeled `private` or `protected[local]` */
   final val PrivateOrLocal = Private | Local
 
+  /** Either a module or a final class */
+  final val ModuleOrFinal = ModuleClass | Final
+
+  /** Either mutable or lazy */
+  final val MutableOrLazy = Mutable | Lazy
+
+  /** Labeled `private` or `final` */
+  final val PrivateOrFinal = Private | Final
+
   /** A type parameter with synthesized name */
   final val ExpandedTypeParam = allOf(ExpandedName, TypeParam)
 

src/dotty/tools/dotc/core/SymDenotations.scala

@@ -586,6 +586,12 @@ object SymDenotations {
     final def enclosingClass(implicit ctx: Context): Symbol =
       if (isClass || !exists) symbol else owner.enclosingClass
 
+    final def isEffectivelyFinal(implicit ctx: Context): Boolean = {
+      (this.flags is Flags.PrivateOrFinal) || (!this.owner.isClass) ||
+        ((this.owner.flags is (Flags.ModuleOrFinal)) && (!this.flags.is(Flags.MutableOrLazy))) ||
+        (this.owner.isAnonymousClass)
+    }
+
     /** The class containing this denotation which has the given effective name.
      */
     final def enclosingClassNamed(name: Name)(implicit ctx: Context): Symbol = {