LibJS: Add Object::may_interfere_with_indexed_property_access() virtual

This function must return true if the object may intercept and customize
access to indexed properties (properties where the property name is a
non-negative integer.)

This will be used to implement fast path optimizations for array-like
accesses in subsequent commits.

Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp

@@ -2573,6 +2573,8 @@ private:
     virtual JS::ThrowCompletionOr<bool> internal_set_prototype_of(JS::Object* prototype) override;
     virtual JS::ThrowCompletionOr<bool> internal_prevent_extensions() override;
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
     JS::Realm& m_realm; // [[Realm]]
 };
 )~~~");

Userland/Libraries/LibJS/Runtime/ArgumentsObject.h

@@ -27,6 +27,8 @@ public:
     virtual ThrowCompletionOr<bool> internal_set(PropertyKey const&, Value value, Value receiver) override;
     virtual ThrowCompletionOr<bool> internal_delete(PropertyKey const&) override;
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
     // [[ParameterMap]]
     Object& parameter_map() { return *m_parameter_map; }
 

Userland/Libraries/LibJS/Runtime/ModuleNamespaceObject.h

@@ -31,6 +31,8 @@ public:
     virtual ThrowCompletionOr<MarkedVector<Value>> internal_own_property_keys() const override;
     virtual void initialize(Realm&) override;
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
 private:
     ModuleNamespaceObject(Realm&, Module* module, Vector<DeprecatedFlyString> exports);
 

Userland/Libraries/LibJS/Runtime/Object.h

@@ -135,6 +135,12 @@ public:
     virtual ThrowCompletionOr<bool> internal_delete(PropertyKey const&);
     virtual ThrowCompletionOr<MarkedVector<Value>> internal_own_property_keys() const;
 
+    // NOTE: Any subclass of Object that overrides property access slots ([[Get]], [[Set]] etc)
+    //       to customize access to indexed properties (properties where the name is a positive integer)
+    //       must return true for this, to opt out of optimizations that rely on assumptions that
+    //       might not hold when property access behaves differently.
+    virtual bool may_interfere_with_indexed_property_access() const { return false; }
+
     ThrowCompletionOr<bool> ordinary_set_with_own_descriptor(PropertyKey const&, Value, Value, Optional<PropertyDescriptor>);
 
     // 10.4.7 Immutable Prototype Exotic Objects, https://tc39.es/ecma262/#sec-immutable-prototype-exotic-objects

Userland/Libraries/LibJS/Runtime/ProxyObject.h

@@ -45,6 +45,8 @@ public:
     virtual ThrowCompletionOr<Value> internal_call(Value this_argument, MarkedVector<Value> arguments_list) override;
     virtual ThrowCompletionOr<NonnullGCPtr<Object>> internal_construct(MarkedVector<Value> arguments_list, FunctionObject& new_target) override;
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
 private:
     ProxyObject(Object& target, Object& handler, Object& prototype);
 

Userland/Libraries/LibJS/Runtime/StringObject.h

@@ -30,6 +30,8 @@ private:
     virtual ThrowCompletionOr<bool> internal_define_own_property(PropertyKey const&, PropertyDescriptor const&) override;
     virtual ThrowCompletionOr<MarkedVector<Value>> internal_own_property_keys() const override;
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
     virtual bool is_string_object() const final { return true; }
     virtual void visit_edges(Visitor&) override;
 

Userland/Libraries/LibJS/Runtime/TypedArray.h

@@ -414,6 +414,8 @@ public:
         return { move(keys) };
     }
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
     ReadonlySpan<UnderlyingBufferDataType> data() const
     {
         return { reinterpret_cast<UnderlyingBufferDataType const*>(m_viewed_array_buffer->buffer().data() + m_byte_offset), m_array_length };

Userland/Libraries/LibWeb/Bindings/LegacyPlatformObject.h

@@ -29,6 +29,8 @@ public:
     virtual JS::ThrowCompletionOr<bool> internal_prevent_extensions() override;
     virtual JS::ThrowCompletionOr<JS::MarkedVector<JS::Value>> internal_own_property_keys() const override;
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
     enum class IgnoreNamedProps {
         No,
         Yes,

Userland/Libraries/LibWeb/HTML/AudioTrackList.h

@@ -51,6 +51,8 @@ private:
     virtual void initialize(JS::Realm&) override;
     virtual JS::ThrowCompletionOr<Optional<JS::PropertyDescriptor>> internal_get_own_property(JS::PropertyKey const& property_name) const override;
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
     JS::MarkedVector<JS::NonnullGCPtr<AudioTrack>> m_audio_tracks;
 };
 

Userland/Libraries/LibWeb/HTML/Location.h

@@ -64,6 +64,8 @@ public:
     virtual JS::ThrowCompletionOr<bool> internal_delete(JS::PropertyKey const&) override;
     virtual JS::ThrowCompletionOr<JS::MarkedVector<JS::Value>> internal_own_property_keys() const override;
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
     HTML::CrossOriginPropertyDescriptorMap const& cross_origin_property_descriptor_map() const { return m_cross_origin_property_descriptor_map; }
     HTML::CrossOriginPropertyDescriptorMap& cross_origin_property_descriptor_map() { return m_cross_origin_property_descriptor_map; }
 

Userland/Libraries/LibWeb/HTML/VideoTrackList.h

@@ -44,6 +44,8 @@ private:
     virtual void initialize(JS::Realm&) override;
     virtual JS::ThrowCompletionOr<Optional<JS::PropertyDescriptor>> internal_get_own_property(JS::PropertyKey const& property_name) const override;
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
     JS::MarkedVector<JS::NonnullGCPtr<VideoTrack>> m_video_tracks;
 };
 

Userland/Libraries/LibWeb/HTML/WindowProxy.h

@@ -31,6 +31,8 @@ public:
     virtual JS::ThrowCompletionOr<bool> internal_delete(JS::PropertyKey const&) override;
     virtual JS::ThrowCompletionOr<JS::MarkedVector<JS::Value>> internal_own_property_keys() const override;
 
+    virtual bool may_interfere_with_indexed_property_access() const final { return true; }
+
     JS::GCPtr<Window> window() const { return m_window; }
     void set_window(JS::NonnullGCPtr<Window>);