From 63d74706850f056d63d5b19465c4cee8d6eab3a7 Mon Sep 17 00:00:00 2001
From: John Wellbelove <john.wellbelove@asterconsulting.co.uk>
Date: Mon, 18 Aug 2025 14:22:33 +0100
Subject: [PATCH] Added etl::nontype_t, with C++11 and C++17 alternatives

---
 include/etl/utility.h | 20 ++++++++++++++++++++
 test/test_utility.cpp | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/include/etl/utility.h b/include/etl/utility.h
index 43852e72..c3ea993d 100644
--- a/include/etl/utility.h
+++ b/include/etl/utility.h
@@ -818,6 +818,26 @@ namespace etl
     TReturn(*ptr)(TArgs...);
   };
 #endif
+
+#if ETL_USING_CPP17 && !defined(ETL_FORCE_CPP11_NONTYPE)
+  //*****************************************************************************
+  // Wraps a non-type template parameter as a type.
+  //*****************************************************************************
+  template <auto Value>
+  struct nontype_t
+  {
+    static constexpr decltype(Value) value = Value;
+  };
+#elif ETL_USING_CPP11
+  //*****************************************************************************
+  // Wraps a non-type template parameter as a type.
+  //*****************************************************************************
+  template <typename T, T Value>
+  struct nontype_t
+  {
+    static constexpr T value = Value;
+  };
+#endif
 }
 
 #endif
diff --git a/test/test_utility.cpp b/test/test_utility.cpp
index 4b378625..0a9559e6 100644
--- a/test/test_utility.cpp
+++ b/test/test_utility.cpp
@@ -789,4 +789,42 @@ namespace
     }
 #endif
   };
+
+#if ETL_USING_CPP17 && !defined(ETL_FORCE_CPP11_NONTYPE)
+  //*********************************
+  TEST(test_nontype_t_cpp17)
+  {
+    // Test with int
+    CHECK_TRUE(42 == etl::nontype_t<42>::value);
+
+    // Test with bool
+    CHECK_TRUE(true == etl::nontype_t<true>::value);
+
+    // Test with char
+    CHECK_TRUE('A' == etl::nontype_t<'A'>::value);
+
+    // Test with enum
+    enum class E : uint8_t { A = 1, B = 2 };
+    CHECK_TRUE(E::A == etl::nontype_t<E::A>::value);
+    CHECK_TRUE(E::B == etl::nontype_t<E::B>::value);
+  }
+#elif ETL_USING_CPP11
+  enum class E : uint8_t { A = 1, B = 2 };
+
+  TEST(test_nontype_t_cpp11)
+  {
+    // Test with int
+    CHECK_TRUE(42 == (etl::nontype_t<int, 42>::value));
+
+    // Test with bool
+    CHECK_TRUE(true == (etl::nontype_t<bool, true>::value));
+
+    // Test with char
+    CHECK_TRUE('A' == (etl::nontype_t<char, 'A'>::value));
+
+    // Test with enum
+    CHECK_TRUE(E::A == (etl::nontype_t<E, E::A>::value));
+    CHECK_TRUE(E::B == (etl::nontype_t<E, E::B>::value));
+  }
+#endif
 }