From 1d481a395ae18546f9bfd224f196a0271a526691 Mon Sep 17 00:00:00 2001
From: Jordan Woyak <jordan.woyak@gmail.com>
Date: Tue, 25 Feb 2025 03:59:37 -0600
Subject: [PATCH] VariantUtil: Introduce WithVariantAlternative to dynamically
 construct and visit a variant alternative.

---
 Source/Core/Common/VariantUtil.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/Source/Core/Common/VariantUtil.h b/Source/Core/Common/VariantUtil.h
index 69f886c167..54ac6ba2cf 100644
--- a/Source/Core/Common/VariantUtil.h
+++ b/Source/Core/Common/VariantUtil.h
@@ -34,3 +34,18 @@ struct overloaded : Ts...
 
 template <class... Ts>
 overloaded(Ts...) -> overloaded<Ts...>;
+
+// Visits a functor with a variant_alternative of the given index.
+// e.g. WithVariantAlternative<variant<int, float>>(1, func) calls func<float>()
+// An out-of-bounds index causes no visitation.
+template <typename Variant, std::size_t I = 0, typename Func>
+void WithVariantAlternative(std::size_t index, Func&& func)
+{
+  if constexpr (I < std::variant_size_v<Variant>)
+  {
+    if (index == 0)
+      func.template operator()<std::variant_alternative_t<I, Variant>>();
+    else
+      WithVariantAlternative<Variant, I + 1>(index - 1, std::forward<Func>(func));
+  }
+}