intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 23 insertions, 0 deletions

diff --git a/util/generic/variant.h b/util/generic/variant.h
new file mode 100644
index 0000000000..749fc75090
--- /dev/null
+++ b/util/generic/variant.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include "hash.h"
+
+#include <variant>
+
+template <class... Ts>
+struct THash<std::variant<Ts...>> {
+public:
+    size_t operator()(const std::variant<Ts...>& v) const noexcept {
+        return CombineHashes(
+            IntHash(v.index()),
+            v.valueless_by_exception() ? 0 : std::visit([](const auto& value) { return ComputeHash(value); }, v));
+    }
+};
+
+template <>
+struct THash<std::monostate> {
+public:
+    constexpr size_t operator()(std::monostate) const noexcept {
+        return 1;
+    }
+};