Minor. Covariantly override ClassDescriptor.original

compiler/frontend/src/org/jetbrains/kotlin/resolve/scopes/receivers/ExpressionReceiver.kt

@@ -59,7 +59,7 @@ interface ExpressionReceiver :  ReceiverValue {
             if (referenceExpression != null) {
                 val descriptor = bindingContext.get(BindingContext.REFERENCE_TARGET, referenceExpression)
                 if (descriptor is ClassDescriptor) {
-                    return ThisExpressionClassReceiver(descriptor.original as ClassDescriptor, expression, type)
+                    return ThisExpressionClassReceiver(descriptor.original, expression, type)
                 }
             }
             else if (expression is KtSuperExpression) {

core/descriptors/src/org/jetbrains/kotlin/descriptors/ClassDescriptor.java

@@ -103,4 +103,8 @@ public interface ClassDescriptor extends ClassifierDescriptor, MemberDescriptor,
     @ReadOnly
     @NotNull
     List<TypeParameterDescriptor> getDeclaredTypeParameters();
+
+    @NotNull
+    @Override
+    ClassDescriptor getOriginal();
 }

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/AbstractClassDescriptor.java

@@ -65,7 +65,7 @@ public abstract class AbstractClassDescriptor implements ClassDescriptor {
 
     @NotNull
     @Override
-    public DeclarationDescriptorWithSource getOriginal() {
+    public ClassDescriptor getOriginal() {
         return this;
     }
 

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/LazySubstitutingClassDescriptor.java

@@ -173,7 +173,7 @@ public class LazySubstitutingClassDescriptor implements ClassDescriptor {
 
     @NotNull
     @Override
-    public DeclarationDescriptorWithSource getOriginal() {
+    public ClassDescriptor getOriginal() {
         return original.getOriginal();
     }