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refactor(templates): add sizeof...(Ts) > 0 constraint to TVariant

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This commit is contained in:
_Redstone_c_ 2022-11-17 18:48:20 +08:00
parent 3f56a2beca
commit 9a3c957b38
1 changed files with 21 additions and 11 deletions
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32
Redcraft.Utility/Source/Public/Templates/Variant.h
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@ -13,14 +13,18 @@ NAMESPACE_REDCRAFT_BEGIN
NAMESPACE_MODULE_BEGIN(Redcraft)
NAMESPACE_MODULE_BEGIN(Utility)
template <typename... Ts> requires (true && ... && CDestructible<Ts>)
template <typename... Ts> requires (sizeof...(Ts) > 0 && (true && ... && CDestructible<Ts>))
class TVariant;
NAMESPACE_PRIVATE_BEGIN
template <typename T > struct TIsTVariant : FFalse { };
template <typename T > struct TIsTVariant : FFalse { };
template <typename... Ts> struct TIsTVariant<TVariant<Ts...>> : FTrue { };
// This class is to avoid conflicting with sizeof...(Ts) > 0 constraints when using TVariant<> in tool templates
template <typename... Ts>
struct TVariantProxy { };
template <typename TupleType>
struct TVariantNumImpl;
@ -40,19 +44,22 @@ template <typename T, typename TupleType>
struct TVariantIndexImpl;
template <typename T, typename U, typename... Ts>
struct TVariantIndexImpl<T, TVariant<U, Ts...>> : TConstant<size_t, TVariantIndexImpl<T, TVariant<Ts...>>::Value + 1>
struct TVariantIndexImpl<T, TVariantProxy<U, Ts...>> : TConstant<size_t, TVariantIndexImpl<T, TVariantProxy<Ts...>>::Value + 1>
{
static_assert(sizeof...(Ts) != 0, "Non-existent types in variant");
};
template <typename T, typename... Ts>
struct TVariantIndexImpl<T, TVariant<T, Ts...>> : TConstant<size_t, 0>
struct TVariantIndexImpl<T, TVariantProxy<T, Ts...>> : TConstant<size_t, 0>
{
static_assert((true && ... && !CSameAs<T, Ts>), "Duplicate type in variant");
};
template <typename T>
struct TVariantIndexImpl<T, TVariant<>> : TConstant<size_t, INDEX_NONE> { };
struct TVariantIndexImpl<T, TVariantProxy<>> : TConstant<size_t, INDEX_NONE> { };
template <typename T, typename... Ts>
struct TVariantIndexImpl<T, TVariant<Ts...>> : TVariantIndexImpl<T, TVariantProxy<Ts...>> { };
template <typename T, typename... Ts>
struct TVariantIndexImpl<T, const TVariant<Ts...>> : TVariantIndexImpl<T, TVariant<Ts...>> { };
@ -67,20 +74,23 @@ template <size_t I, typename TupleType>
struct TVariantAlternativeImpl;
template <size_t I, typename T, typename... Ts>
struct TVariantAlternativeImpl<I, TVariant<T, Ts...>>
struct TVariantAlternativeImpl<I, TVariantProxy<T, Ts...>>
{
static_assert(I < sizeof...(Ts) + 1, "Invalid index in variant");
using Type = TVariantAlternativeImpl<I - 1, TVariant<Ts...>>::Type;
using Type = TVariantAlternativeImpl<I - 1, TVariantProxy<Ts...>>::Type;
};
template <typename T, typename... Ts>
struct TVariantAlternativeImpl<0, TVariant<T, Ts...>> { using Type = T; };
struct TVariantAlternativeImpl<0, TVariantProxy<T, Ts...>> { using Type = T; };
template <size_t I, typename... Ts>
struct TVariantAlternativeImpl<I, TVariant<Ts...>> { };
struct TVariantAlternativeImpl<I, TVariantProxy<Ts...>> { };
template <>
struct TVariantAlternativeImpl<0, TVariant<>> { };
struct TVariantAlternativeImpl<0, TVariantProxy<>> { };
template <size_t I, typename... Ts>
struct TVariantAlternativeImpl<I, TVariant<Ts...>> : TVariantAlternativeImpl<I, TVariantProxy<Ts...>> { };
template <size_t I, typename... Ts>
struct TVariantAlternativeImpl<I, const TVariant<Ts...>> { using Type = TAddConst<typename TVariantAlternativeImpl<I, TVariant<Ts...>>::Type>; };
@ -138,7 +148,7 @@ inline constexpr size_t TVariantIndex = NAMESPACE_PRIVATE::TVariantIndexImpl<T,
template <size_t I, typename VariantType>
using TVariantAlternative = typename NAMESPACE_PRIVATE::TVariantAlternativeImpl<I, VariantType>::Type;
template <typename... Ts> requires (true && ... && CDestructible<Ts>)
template <typename... Ts> requires (sizeof...(Ts) > 0 && (true && ... && CDestructible<Ts>))
class TVariant
{
public: