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 06/10] 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 d06d32dac6c7b6faeedefeaa107cedac8446a3ab..1957fc0339b5538fbdc56a8ea2d8503c89ed4b59 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.
@@ -64,7 +64,7 @@ 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 8786d6d64ac44ac88133df65a79636ec133b1b64..d1bf7e62aa844003cfcd7f3df6fd9c9a65563586 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.
@@ -96,7 +96,7 @@ 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