PersistedAssemblyBuilder missing methods on generated types

src/libraries/System.Reflection.Emit/ref/System.Reflection.Emit.cs

@@ -660,7 +660,7 @@ public void DefineMethodOverride(System.Reflection.MethodInfo methodInfoBody, Sy
         [System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.NonPublicProperties | System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.PublicProperties)]
         public override System.Reflection.PropertyInfo[] GetProperties(System.Reflection.BindingFlags bindingAttr) { throw null; }
         [System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.NonPublicProperties | System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.PublicProperties)]
-        protected override System.Reflection.PropertyInfo GetPropertyImpl(string name, System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder? binder, System.Type? returnType, System.Type[]? types, System.Reflection.ParameterModifier[]? modifiers) { throw null; }
+        protected override System.Reflection.PropertyInfo? GetPropertyImpl(string name, System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder? binder, System.Type? returnType, System.Type[]? types, System.Reflection.ParameterModifier[]? modifiers) { throw null; }
         protected override bool HasElementTypeImpl() { throw null; }
         [System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.All)]
         public override object? InvokeMember(string name, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder? binder, object? target, object?[]? args, System.Reflection.ParameterModifier[]? modifiers, System.Globalization.CultureInfo? culture, string[]? namedParameters) { throw null; }

src/libraries/System.Reflection.Emit/src/System/Reflection/Emit/ModuleBuilderImpl.cs

@@ -1381,5 +1381,19 @@ protected override ISymbolDocumentWriter DefineDocumentCore(string url, Guid lan
         {
             return new SymbolDocumentWriter(url, language);
         }
+
+        internal List<TypeBuilderImpl> GetNestedTypeBuilders(TypeBuilderImpl declaringType)
+        {
+            List<TypeBuilderImpl> nestedTypes = new List<TypeBuilderImpl>();
+            foreach (TypeBuilderImpl typeBuilder in _typeDefinitions)
+            {
+                if (typeBuilder.DeclaringType == declaringType)
+                {
+                    nestedTypes.Add(typeBuilder);
+                }
+            }
+
+            return nestedTypes;
+        }
     }
 }