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[ADT] Backport std::to_underlying from C++23 #70681

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Merged
Endilll merged 6 commits into from
Oct 30, 2023
Merged

[ADT] Backport std::to_underlying from C++23 #70681

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a83117a
[STLExtras] Backport std::to_underlying from C++23
Endilll Oct 30, 2023
1fdc702
Run clang-format
Endilll Oct 30, 2023
a6c4963
Move changes from STLExtras to STLForwardCompat
Endilll Oct 30, 2023
c1df3bc
Add description of function
Endilll Oct 30, 2023
daef3cc
Remove unnecessary `typename` keyword
Endilll Oct 30, 2023
3e41646
Run clang-format
Endilll Oct 30, 2023
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7 changes: 7 additions & 0 deletions llvm/include/llvm/ADT/STLForwardCompat.h
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,13 @@ auto transformOptional(std::optional<T> &&O, const Function &F)
return std::nullopt;
}

/// Returns underlying integer value of an enum. Backport of C++23
/// std::to_underlying.
template <typename Enum>
[[nodiscard]] constexpr std::underlying_type_t<Enum> to_underlying(Enum E) {
return static_cast<std::underlying_type_t<Enum>>(E);
}

} // namespace llvm

#endif // LLVM_ADT_STLFORWARDCOMPAT_H
17 changes: 17 additions & 0 deletions llvm/unittests/ADT/STLForwardCompatTest.cpp
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Expand Up @@ -119,4 +119,21 @@ TEST(TransformTest, MoveTransformLlvm) {
EXPECT_EQ(0u, MoveOnly::Destructions);
}

TEST(TransformTest, ToUnderlying) {
enum E { A1 = 0, B1 = -1 };
static_assert(llvm::to_underlying(A1) == 0);
static_assert(llvm::to_underlying(B1) == -1);

enum E2 : unsigned char { A2 = 0, B2 };
static_assert(
std::is_same_v<unsigned char, decltype(llvm::to_underlying(A2))>);
static_assert(llvm::to_underlying(A2) == 0);
static_assert(llvm::to_underlying(B2) == 1);

enum class E3 { A3 = -1, B3 };
static_assert(std::is_same_v<int, decltype(llvm::to_underlying(E3::A3))>);
static_assert(llvm::to_underlying(E3::A3) == -1);
static_assert(llvm::to_underlying(E3::B3) == 0);
}

} // namespace