Add std::hash specialization for rich-enums

teslamotors · Sep 12, 2024 · 97800b0 · 97800b0
1 parent 5d624d8
commit 97800b0
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diff --git a/include/fixed_containers/enum_utils.hpp b/include/fixed_containers/enum_utils.hpp
@@ -635,3 +635,13 @@ class NonDefaultConstructibleSkeletalRichEnum
 };
 
 }  // namespace fixed_containers::rich_enums
+
+template <fixed_containers::rich_enums::is_rich_enum RichEnumType>
+struct std::hash<RichEnumType>
+{
+    // std::hash<BackingEnum> is not constexpr
+    /*constexpr*/ std::size_t operator()(const RichEnumType& val) const noexcept
+    {
+        return std::hash<typename RichEnumType::BackingEnum>{}(val.backing_enum());
+    }
+};
diff --git a/test/enum_utils_test.cpp b/test/enum_utils_test.cpp
@@ -318,6 +318,34 @@ TEST(RichEnum, BoolNegate)
     }
 }
 
+TEST(RichEnum, StdHash)
+{
+    {
+        std::size_t hash_value_of_backing_enum =
+            std::hash<detail::TestRichEnum1BackingEnum>{}(detail::TestRichEnum1BackingEnum::C_ONE);
+        std::size_t hash_value_of_rich_enum = std::hash<TestRichEnum1>{}(TestRichEnum1::C_ONE());
+        ASSERT_EQ(hash_value_of_backing_enum, hash_value_of_rich_enum);
+    }
+    {
+        std::size_t hash_value_of_backing_enum =
+            std::hash<detail::TestRichEnum1BackingEnum>{}(detail::TestRichEnum1BackingEnum::C_TWO);
+        std::size_t hash_value_of_rich_enum = std::hash<TestRichEnum1>{}(TestRichEnum1::C_TWO());
+        ASSERT_EQ(hash_value_of_backing_enum, hash_value_of_rich_enum);
+    }
+    {
+        std::size_t hash_value_of_backing_enum = std::hash<detail::TestRichEnum1BackingEnum>{}(
+            detail::TestRichEnum1BackingEnum::C_THREE);
+        std::size_t hash_value_of_rich_enum = std::hash<TestRichEnum1>{}(TestRichEnum1::C_THREE());
+        ASSERT_EQ(hash_value_of_backing_enum, hash_value_of_rich_enum);
+    }
+    {
+        std::size_t hash_value_of_backing_enum =
+            std::hash<detail::TestRichEnum1BackingEnum>{}(detail::TestRichEnum1BackingEnum::C_FOUR);
+        std::size_t hash_value_of_rich_enum = std::hash<TestRichEnum1>{}(TestRichEnum1::C_FOUR());
+        ASSERT_EQ(hash_value_of_backing_enum, hash_value_of_rich_enum);
+    }
+}
+
 static_assert(IsStructuralType<TestRichEnum1>);
 
 namespace