6 files changed, 16 insertions, 15 deletions
diff --git a/src/kernel/NeKit/Nullable.h b/src/kernel/NeKit/Domain.h
index 30ce9da4..cda63ee9 100644
--- a/src/kernel/NeKit/Nullable.h
+++ b/src/kernel/NeKit/Domain.h
@@ -4,8 +4,8 @@
 
 ======================================== */
 
-#ifndef __NE_KIT_NULLABLE_H__
-#define __NE_KIT_NULLABLE_H__
+#ifndef __NE_KIT_DOMAIN_H__
+#define __NE_KIT_DOMAIN_H__
 
 #include <NeKit/Config.h>
 
@@ -23,10 +23,15 @@ struct IsDefined<nullPtr> final {
   static constexpr bool kValue = false;
 };
 
+using NullDomain = IsDefined<nullPtr>;
+
+template <class Type>
+using Domain = IsDefined<Type>;
+
 template <class Type>
 concept IsAcceptable = requires() {
   { IsDefined<Type>::kValue };
 };
 }  // namespace Kernel
 
-#endif  // !__NE_KIT_NULLABLE_H__
-\ No newline at end of file
+#endif  // !__NE_KIT_DOMAIN_H__
+\ No newline at end of file
diff --git a/src/kernel/NeKit/Function.h b/src/kernel/NeKit/Function.h
index f7e47973..dfa8608a 100644
--- a/src/kernel/NeKit/Function.h
+++ b/src/kernel/NeKit/Function.h
@@ -27,8 +27,6 @@ class Function final {
 
   T operator()(Args&&... args) { return fFn(args...); }
 
-  T Call(Args&&... args) { return fFn(args...); }
-
   explicit operator bool() { return fFn; }
   bool     operator!() { return !fFn; }
 
diff --git a/src/kernel/NeKit/Ref.h b/src/kernel/NeKit/Ref.h
index 62460568..4767f728 100644
--- a/src/kernel/NeKit/Ref.h
+++ b/src/kernel/NeKit/Ref.h
@@ -12,7 +12,7 @@
 #include <KernelKit/HeapMgr.h>
 #include <NeKit/Config.h>
 #include <NeKit/KernelPanic.h>
-#include <NeKit/Nullable.h>
+#include <NeKit/Domain.h>
 #include <NeKit/Vettable.h>
 
 namespace Kernel {
diff --git a/src/kernel/NeKit/TOML.h b/src/kernel/NeKit/TOML.h
index dee273ad..3eaf5197 100644
--- a/src/kernel/NeKit/TOML.h
+++ b/src/kernel/NeKit/TOML.h
@@ -6,6 +6,8 @@
 
 #pragma once
 
+#include <NeKit/Config.h>
+
 namespace Kernel {
 class TOMLObject final {
  public:
diff --git a/src/kernel/NeKit/Variant.h b/src/kernel/NeKit/Variant.h
index f7b2c450..5747e9ca 100644
--- a/src/kernel/NeKit/Variant.h
+++ b/src/kernel/NeKit/Variant.h
@@ -40,13 +40,9 @@ class Variant final {
       : fPtr((VoidPtr) stringView), fKind(VariantKind::kString) {}
 
   explicit Variant(JsonObject<>* json) : fPtr((VoidPtr) json), fKind(VariantKind::kJson) {}
-
   explicit Variant(TOMLObject* toml) : fPtr((VoidPtr) toml), fKind(VariantKind::kTOML) {}
-
   explicit Variant(nullPtr ptr) : fPtr(ptr), fKind(VariantKind::kNull) {}
-
-  explicit Variant(SWAP_DISK_HEADER* ptr) : fPtr(ptr), fKind(VariantKind::kSwap) {}
-
+  explicit Variant(SwapDiskHdr* ptr) : fPtr(ptr), fKind(VariantKind::kSwap) {}
   explicit Variant(VoidPtr ptr) : fPtr(ptr), fKind(VariantKind::kBlob) {}
 
  public:
diff --git a/src/kernel/NeKit/Vettable.h b/src/kernel/NeKit/Vettable.h
index fad1f06c..d79aaa0b 100644
--- a/src/kernel/NeKit/Vettable.h
+++ b/src/kernel/NeKit/Vettable.h
@@ -39,12 +39,12 @@ struct Vettable<IVettable> final {
   static constexpr bool kValue = true;
 };
 
-using FallbackType = bool (*)(bool type_value);
+template <class Type>
+using FallbackType = Void (*)(const PropertyResult<Type>& type_value);
 
-/// @brief Concept version of Vettable.
-template <typename Type, FallbackType OnFallback>
+template <class Type, FallbackType<Type> OnFallback>
 concept IsVettable = requires() {
-  { Vettable<Type>::kValue ? TrueResult<Type>::kValue : OnFallback(PropertyResult<Type>::kValue) };
+  { Vettable<Type>::kValue ? TrueResult<Type>{} : OnFallback(PropertyResult<Type>{}) };
 };
 }  // namespace Kernel