avm2: Make missing props on sealed classes throw properly

core/src/avm2/object/script_object.rs

@@ -166,11 +166,19 @@ impl<'gc> ScriptObjectData<'gc> {
         };
 
         let value = self.values.get(&local_name);
-
         if let Some(value) = value {
             return Ok(*value);
-        } else if let Some(proto) = self.proto() {
+        }
-            return proto.get_property_local(multiname, activation);
+
+        // follow the prototype chain
+        let mut proto = self.proto();
+        while let Some(obj) = proto {
+            let obj = obj.base();
+            let value = obj.values.get(&local_name);
+            if let Some(value) = value {
+                return Ok(*value);
+            }
+            proto = obj.proto();
         }
 
         // Special case: Unresolvable properties on dynamic classes are treated

tests/tests/swfs/avm2/es4_oop_prototypes/Test.as

@@ -1,5 +1,11 @@
-package {
+// compiled with mxmlc
-	public class Test {}
+
+package {
+    import flash.display.MovieClip;
+    public class Test extends MovieClip {
+        public function Test() {
+        }
+    }
 }
 
 class ES4Class extends Object {
@@ -51,3 +57,22 @@ x.test_method();
 ES4Class.test_static();
 x.test_proto_method();
 trace(x.test_get);
+
+trace("-----------------")
+
+class SealedClass{}
+SealedClass.prototype.field = 1;
+x = new SealedClass();
+trace(x.field);
+try {
+	trace(x.nofield);
+} catch (e) {
+	trace("Caught missing field")
+}
+
+dynamic class DynamicClass{}
+DynamicClass.prototype.field = 1;
+x = new DynamicClass();
+trace(x.field);
+trace(x.nofield);
+

tests/tests/swfs/avm2/es4_oop_prototypes/output.txt

@@ -6,3 +6,8 @@ ES4Class test_method
 ES4Class test_static
 ES4Class test_proto_method
 ES4Class test_get
+-----------------
+1
+Caught missing field
+1
+undefined