Add proto chain inspection to the object interface.

core/src/avm1/globals/object.rs

@@ -105,19 +105,14 @@ fn is_prototype_of<'gc>(
                 Ok(ob) => ob,
                 Err(_) => return Ok(Value::Bool(false).into()),
             };
-            let mut proto = ob.read().as_script_object().unwrap().prototype().cloned();
+            let mut proto = ob.read().proto();
 
             while let Some(proto_ob) = proto {
                 if GcCell::ptr_eq(this, proto_ob) {
                     return Ok(Value::Bool(true).into());
                 }
 
-                proto = proto_ob
+                proto = proto_ob.read().proto();
-                    .read()
-                    .as_script_object()
-                    .unwrap()
-                    .prototype()
-                    .cloned();
             }
 
             Ok(Value::Bool(false).into())

core/src/avm1/object.rs

@@ -75,6 +75,13 @@ pub trait Object<'gc>: 'gc + Collect + Debug {
     /// Returns false if the property cannot be deleted.
     fn delete(&mut self, name: &str) -> bool;
 
+    /// Retrieve the `__proto__` of a given object.
+    ///
+    /// The proto is another object used to resolve methods across a class of
+    /// multiple objects. It should also be accessible as `__proto__` from
+    /// `get`.
+    fn proto(&self) -> Option<ObjectCell<'gc>>;
+
     /// Checks if the object has a given named property.
     fn has_property(&self, name: &str) -> bool;
 

core/src/avm1/script_object.rs

@@ -204,10 +204,6 @@ impl<'gc> ScriptObject<'gc> {
         self.prototype = Some(prototype);
     }
 
-    pub fn prototype(&self) -> Option<&ObjectCell<'gc>> {
-        self.prototype.as_ref()
-    }
-
     pub fn set_type_of(&mut self, type_of: &'static str) {
         self.type_of = type_of;
     }
@@ -332,6 +328,10 @@ impl<'gc> Object<'gc> for ScriptObject<'gc> {
         false
     }
 
+    fn proto(&self) -> Option<ObjectCell<'gc>> {
+        self.prototype
+    }
+
     /// Checks if the object has a given named property.
     fn has_property(&self, name: &str) -> bool {
         self.has_own_property(name)