From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Tyler Veness <calcmogul@gmail.com>
Date: Wed, 3 Dec 2025 23:38:53 -0800
Subject: [PATCH 6/9] Replace std::unreachable()

---
 include/sleipnir/autodiff/expression_type.hpp    |  6 +++---
 .../sleipnir/optimization/solver/exit_status.hpp |  6 +++---
 include/sleipnir/util/unreachable.hpp            | 16 ++++++++++++++++
 3 files changed, 22 insertions(+), 6 deletions(-)
 create mode 100644 include/sleipnir/util/unreachable.hpp

diff --git a/include/sleipnir/autodiff/expression_type.hpp b/include/sleipnir/autodiff/expression_type.hpp
index 2fde6bdf3cf72f46fb633b72e29e66209e9f6a83..8a2ae457808b1ae505c19c8f65a5c68e6e11a082 100644
--- a/include/sleipnir/autodiff/expression_type.hpp
+++ b/include/sleipnir/autodiff/expression_type.hpp
@@ -4,10 +4,10 @@
 
 #include <stdint.h>
 
-#include <utility>
-
 #include <fmt/base.h>
 
+#include "sleipnir/util/unreachable.hpp"
+
 namespace slp {
 
 /// Expression type.
@@ -61,7 +61,7 @@ struct fmt::formatter<slp::ExpressionType> {
       case NONLINEAR:
         return m_underlying.format("nonlinear", ctx);
       default:
-        std::unreachable();
+        slp::unreachable();
     }
   }
 
diff --git a/include/sleipnir/optimization/solver/exit_status.hpp b/include/sleipnir/optimization/solver/exit_status.hpp
index c1e4d319c197bdad2ace19500fb3a0426060e87b..4d43cea244afd6c8b0235b84e9140359451fbf2f 100644
--- a/include/sleipnir/optimization/solver/exit_status.hpp
+++ b/include/sleipnir/optimization/solver/exit_status.hpp
@@ -4,10 +4,10 @@
 
 #include <stdint.h>
 
-#include <utility>
-
 #include <fmt/base.h>
 
+#include "sleipnir/util/unreachable.hpp"
+
 namespace slp {
 
 /// Solver exit status. Negative values indicate failure.
@@ -88,7 +88,7 @@ struct fmt::formatter<slp::ExitStatus> {
       case TIMEOUT:
         return m_underlying.format("timeout", ctx);
       default:
-        std::unreachable();
+        slp::unreachable();
     }
   }
 
diff --git a/include/sleipnir/util/unreachable.hpp b/include/sleipnir/util/unreachable.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..2e5ec3e716b36e892476fb3accafacbb1ba1fa7d
--- /dev/null
+++ b/include/sleipnir/util/unreachable.hpp
@@ -0,0 +1,16 @@
+// Copyright (c) Sleipnir contributors
+
+#pragma once
+
+namespace slp {
+
+[[noreturn]]
+inline void unreachable() {
+#if defined(_MSC_VER) && !defined(__clang__)
+  __assume(false);
+#else
+  __builtin_unreachable();
+#endif
+}
+
+}  // namespace slp