Fixes aws#3353

packages/@jsii/go-runtime/jsii-runtime-go/cast.go

@@ -43,7 +43,7 @@ func UnsafeCast(from interface{}, into interface{}) {
 	client := kernel.GetClient()
 	if objID, found := client.FindObjectRef(rfrom); found {
 		// Ensures the value is initialized properly. Panics if the target value is not a jsii interface type.
-		client.Types().InitJsiiProxy(rinto)
+		client.Types().InitJsiiProxy(rinto, rinto.Type())
 
 		// If the target type is a behavioral interface, add it to the ObjectRef.Interfaces list.
 		if fqn, found := client.Types().InterfaceFQN(rinto.Type()); found {

packages/@jsii/go-runtime/jsii-runtime-go/internal/kernel/conversions.go

@@ -63,14 +63,19 @@ func (c *Client) castAndSetToPtr(ptr reflect.Value, data reflect.Value) {
 			return
 		}
 
+		targetType := ptr.Type()
+		if typ, ok := c.Types().FindType(ref.TypeFQN()); ok && typ.AssignableTo(ptr.Type()) {
+			targetType = typ
+		}
+
 		// If it's currently tracked, return the current instance
-		if object, ok := c.objects.GetObjectAs(ref.InstanceID, ptr.Type()); ok {
+		if object, ok := c.objects.GetObjectAs(ref.InstanceID, targetType); ok {
 			ptr.Set(object)
 			return
 		}
 
 		// If return data is jsii object references, add to objects table.
-		if err := c.Types().InitJsiiProxy(ptr); err == nil {
+		if err := c.Types().InitJsiiProxy(ptr, targetType); err == nil {
 			if err = c.RegisterInstance(ptr, ref); err != nil {
 				panic(err)
 			}

packages/@jsii/go-runtime/jsii-runtime-go/internal/typeregistry/typeregistry.go

@@ -89,9 +89,7 @@ func (t *TypeRegistry) FindType(fqn api.FQN) (typ reflect.Type, ok bool) {
 // InitJsiiProxy initializes a jsii proxy value at the provided pointer. It
 // returns an error if the pointer does not have a value of a registered
 // proxyable type (that is, a class or interface type).
-func (t *TypeRegistry) InitJsiiProxy(val reflect.Value) error {
-	valType := val.Type()
-
+func (t *TypeRegistry) InitJsiiProxy(val reflect.Value, valType reflect.Type) error {
 	switch valType.Kind() {
 	case reflect.Interface:
 		if maker, ok := t.proxyMakers[valType]; ok {
@@ -115,7 +113,7 @@ func (t *TypeRegistry) InitJsiiProxy(val reflect.Value) error {
 			if !field.Anonymous {
 				return fmt.Errorf("refusing to initialize non-anonymous field %s of %v", field.Name, val)
 			}
-			if err := t.InitJsiiProxy(val.Field(i)); err != nil {
+			if err := t.InitJsiiProxy(val.Field(i), field.Type); err != nil {
 				return err
 			}
 		}

packages/@jsii/go-runtime/jsii-runtime-go/runtime/runtime.go

@@ -102,7 +102,7 @@ func RegisterStruct(fqn FQN, strct reflect.Type) {
 // element of it is not a registered jsii interface or class type).
 func InitJsiiProxy(ptr interface{}) {
 	ptrVal := reflect.ValueOf(ptr).Elem()
-	if err := kernel.GetClient().Types().InitJsiiProxy(ptrVal); err != nil {
+	if err := kernel.GetClient().Types().InitJsiiProxy(ptrVal, ptrVal.Type()); err != nil {
 		panic(err)
 	}
 }
@@ -127,7 +127,7 @@ func Create(fqn FQN, args []interface{}, inst interface{}) {
 			if !fieldVal.IsNil() {
 				continue
 			}
-			if err := client.Types().InitJsiiProxy(fieldVal); err != nil {
+			if err := client.Types().InitJsiiProxy(fieldVal, fieldVal.Type()); err != nil {
 				panic(err)
 			}
 
@@ -136,7 +136,7 @@ func Create(fqn FQN, args []interface{}, inst interface{}) {
 			if !fieldVal.IsZero() {
 				continue
 			}
-			if err := client.Types().InitJsiiProxy(fieldVal); err != nil {
+			if err := client.Types().InitJsiiProxy(fieldVal, fieldVal.Type()); err != nil {
 				panic(err)
 			}
 		}