feat: New Nullable system, and improved Vettable system.

Signed-off-by: Amlal El Mahrouss <amlal@nekernel.org>

5 files changed, 58 insertions, 15 deletions

diff --git a/src/kernel/NeKit/Config.h b/src/kernel/NeKit/Config.h
index 39f40401..900ea28c 100644
--- a/src/kernel/NeKit/Config.h
+++ b/src/kernel/NeKit/Config.h
@@ -189,7 +189,12 @@ class ISchedulable {
 };
 
 template <class Type>
-struct FalseResult final {};
+struct FalseResult final {
+  using ResultType    = Type;
+  using ResultTypeRef = ResultType&;
+
+  static constexpr bool kValue = false;
+};
 
 template <class Type>
 struct TrueResult final {
diff --git a/src/kernel/NeKit/ErrorOr.h b/src/kernel/NeKit/ErrorOr.h
index 4e43cb27..5fa8054b 100644
--- a/src/kernel/NeKit/ErrorOr.h
+++ b/src/kernel/NeKit/ErrorOr.h
@@ -25,10 +25,15 @@ class ErrorOr final {
  public:
   using RefType = Ref<T>;
   using Type    = T;
+  using TypePtr = T*;
+
+  explicit ErrorOr(ErrorT err) : mRef((T*) RTL_ALLOCA(sizeof(T))), mId(err) {
+    // AMLALE: Invalidate the value of mRef to make computational evaluations false.
+    mRef = nullptr;
+  }
 
-  explicit ErrorOr(ErrorT err) : mRef((T*) RTL_ALLOCA(sizeof(T))), mId(err) {}
   explicit ErrorOr(nullPtr) {}
-  explicit ErrorOr(Type* klass) : mRef(klass) {}
+  explicit ErrorOr(TypePtr klass) : mRef(klass) {}
   explicit ErrorOr(Type klass) : mRef(klass) {}
 
   ErrorOr& operator=(const ErrorOr&) = default;
diff --git a/src/kernel/NeKit/Nullable.h b/src/kernel/NeKit/Nullable.h
new file mode 100644
index 00000000..c17009fc
--- /dev/null
+++ b/src/kernel/NeKit/Nullable.h
@@ -0,0 +1,26 @@
+#ifndef __NE_KIT_NULLABLE_H__
+#define __NE_KIT_NULLABLE_H__
+
+#include <NeKit/Config.h>
+
+namespace Kernel {
+template <class Type>
+struct IsDefined final {
+  using ResultType    = Type;
+  using ResultTypeRef = Type&;
+
+  static constexpr bool kValue = true;
+};
+
+template <>
+struct IsDefined<nullPtr> final {
+  static constexpr bool kValue = false;
+};
+
+template <class Type>
+concept IsAcceptable = requires() {
+  { IsDefined<Type>::kValue };
+};
+}  // namespace Kernel
+
+#endif  // !__NE_KIT_NULLABLE_H__
\ No newline at end of file
diff --git a/src/kernel/NeKit/Ref.h b/src/kernel/NeKit/Ref.h
index 25706437..62460568 100644
--- a/src/kernel/NeKit/Ref.h
+++ b/src/kernel/NeKit/Ref.h
@@ -12,6 +12,7 @@
 #include <KernelKit/HeapMgr.h>
 #include <NeKit/Config.h>
 #include <NeKit/KernelPanic.h>
+#include <NeKit/Nullable.h>
 #include <NeKit/Vettable.h>
 
 namespace Kernel {
@@ -30,6 +31,13 @@ class Ref final {
   Ref(Type* cls) : fClass(*cls) {}
   Ref(Type cls) : fClass(cls) {}
 
+  Ref& operator=(nullPtr) { return *this; }
+
+  Ref& operator=(Type* ref) {
+    fClass = *ref;
+    return *this;
+  }
+
   Ref& operator=(Type ref) {
     fClass = ref;
     return *this;
@@ -59,11 +67,13 @@ class NonNullRef final {
   using RefType = Ref<T>;
   using Type    = T;
 
-  NonNullRef()        = delete;
-  NonNullRef(nullPtr) = delete;
+  NonNullRef() = delete;
+
+  NonNullRef(Type* ref) : fRef(ref) {}
+
+  NonNullRef(nullPtr ref) = delete;
 
-  NonNullRef(Type* ref) : fRef(ref) { MUST_PASS(ref); }
-  NonNullRef(RefType ref) : fRef(ref) { MUST_PASS(ref); }
+  NonNullRef(RefType ref) : fRef(ref) {}
 
   Ref<T>& operator->() {
     MUST_PASS(fRef);
diff --git a/src/kernel/NeKit/Vettable.h b/src/kernel/NeKit/Vettable.h
index 04d51b1d..c8c27fe3 100644
--- a/src/kernel/NeKit/Vettable.h
+++ b/src/kernel/NeKit/Vettable.h
@@ -40,15 +40,12 @@ struct Vettable<IVettable> final {
   static constexpr bool kValue = true;
 };
 
-/// @brief Concept version of Vettable.
-template <typename Type, typename OnFallback>
-concept IsVettable = requires(OnFallback fallback) {
-  { Vettable<Type>::kValue ? TrueResult<Type>::kValue : fallback() };
-};
+using FallbackType = bool (*)(bool);
 
-template <class Type, typename OnFallback>
-concept IsNotVettable = requires(OnFallback fallback) {
-  { !Vettable<Type>::kValue ? TrueResult<Type>::kValue : fallback() };
+/// @brief Concept version of Vettable.
+template <typename Type, FallbackType OnFallback>
+concept IsVettable = requires() {
+  { Vettable<Type>::kValue ? TrueResult<Type>::kValue : OnFallback(FalseResult<Type>::kValue) };
 };
 }  // namespace Kernel