Changes required for serialization plugin to work:

* Support for generation of synthetic nested classes (for implementations
of user-defined serial annotations):

    1. Compiler extenstion points for contributing names and descriptoprs
of nested classes

    2. Control on synthetic class primary constructor visibility

* Public functions for generating initializing expressions for optional
properties

compiler/backend/src/org/jetbrains/kotlin/codegen/ClassBodyCodegen.java

@@ -27,8 +27,11 @@ import org.jetbrains.kotlin.psi.synthetics.SyntheticClassOrObjectDescriptor;
 import org.jetbrains.kotlin.psi.synthetics.SyntheticClassOrObjectDescriptorKt;
 import org.jetbrains.kotlin.resolve.BindingContext;
 import org.jetbrains.kotlin.resolve.DescriptorUtils;
+import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter;
+import org.jetbrains.kotlin.resolve.scopes.MemberScope;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 
@@ -101,6 +104,16 @@ public abstract class ClassBodyCodegen extends MemberCodegen<KtPureClassOrObject
             genSyntheticClassOrObject((SyntheticClassOrObjectDescriptor) companionObjectDescriptor);
         }
 
+        // Generate synthetic nested classes
+        Collection<DeclarationDescriptor> classifiers = descriptor
+                .getUnsubstitutedMemberScope()
+                .getContributedDescriptors(DescriptorKindFilter.CLASSIFIERS, MemberScope.Companion.getALL_NAME_FILTER());
+        for (DeclarationDescriptor memberDescriptor : classifiers) {
+            if (memberDescriptor instanceof SyntheticClassOrObjectDescriptor) {
+                genSyntheticClassOrObject((SyntheticClassOrObjectDescriptor) memberDescriptor);
+            }
+        }
+
         if (generateNonClassMembers) {
             generateBridges();
         }
@@ -182,7 +195,7 @@ public abstract class ClassBodyCodegen extends MemberCodegen<KtPureClassOrObject
     }
 
     @NotNull
-    protected List<KtParameter> getPrimaryConstructorParameters() {
+    public List<KtParameter> getPrimaryConstructorParameters() {
         if (myClass instanceof KtClass) {
             return myClass.getPrimaryConstructorParameters();
         }

compiler/backend/src/org/jetbrains/kotlin/codegen/MemberCodegen.java

@@ -516,7 +516,8 @@ public abstract class MemberCodegen<T extends KtPureElement/* TODO: & KtDeclarat
     public void beforeMethodBody(@NotNull MethodVisitor mv) {
     }
 
-    private void initializeProperty(@NotNull ExpressionCodegen codegen, @NotNull KtProperty property) {
+    // Requires public access, because it is used by serialization plugin to generate initializer in synthetic constructor
+    public void initializeProperty(@NotNull ExpressionCodegen codegen, @NotNull KtProperty property) {
         PropertyDescriptor propertyDescriptor = (PropertyDescriptor) bindingContext.get(VARIABLE, property);
         assert propertyDescriptor != null;
 
@@ -541,7 +542,8 @@ public abstract class MemberCodegen<T extends KtPureElement/* TODO: & KtDeclarat
         propValue.store(delegateValue, codegen.v);
     }
 
-    protected boolean shouldInitializeProperty(@NotNull KtProperty property) {
+    // Public accessible for serialization plugin to check whether call to initializeProperty(..) is legal.
+    public boolean shouldInitializeProperty(@NotNull KtProperty property) {
         if (!property.hasDelegateExpressionOrInitializer()) return false;
 
         PropertyDescriptor propertyDescriptor = (PropertyDescriptor) bindingContext.get(VARIABLE, property);