Update copyright year

Turns off clang-format for easier usage in projects using it.

.github/FUNDING.yml

@@ -0,0 +1 @@
+github: aantron

LICENSE.md

@@ -0,0 +1,23 @@
+Copyright (c) 2012-2024, Anton Bachin
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+this list of conditions and the following disclaimer in the documentation and/or
+other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

@@ -1,7 +1,5 @@
-# Better Enums   [![version 0.11.2][version]][releases] [![Try online][wandbox-img]][wandbox] [![Travis status][travis-img]][travis] [![AppVeyor status][appveyor-img]][appveyor] [![BSD license][license-img]][license]
+# Better Enums   [![Try online][wandbox-img]][wandbox] [![Travis status][travis-img]][travis] [![AppVeyor status][appveyor-img]][appveyor]
 
-[version]:      https://img.shields.io/badge/version-0.11.2-blue.svg
-[releases]:     https://github.com/aantron/better-enums/releases
 [wandbox]:      http://melpon.org/wandbox/permlink/2QCi3cwQnplAToge
 [wandbox-img]:  https://img.shields.io/badge/try%20it-online-blue.svg
 [appveyor]:     https://ci.appveyor.com/project/aantron/better-enums/branch/master
@@ -98,27 +96,8 @@ a comparison:
 
 <br/>
 
-## Contact and development
-
-Don't hesitate to contact me about features or bugs:
-[antonbachin@yahoo.com][email], or open an issue on GitHub.
-
-If you'd like to help develop Better Enums, see [`CONTRIBUTING`][contributing].
-One area that could use fresh ideas is finding a compile-time data structure
-that both compiles quickly and allows lookup in sub-linear time.
-
-[email]:        mailto:antonbachin@yahoo.com
-[contributing]: https://github.com/aantron/better-enums/blob/master/doc/CONTRIBUTING.md
-
-<br/>
-
-## License and history
-
-Better Enums is released under the BSD 2-clause license. See
-[`LICENSE`][license].
+## History
 
 The original version of the library was developed by the author in the winter of
 2012-2013 at Hudson River Trading, as a replacement for an older generator
 called `BETTER_ENUM`.
-
-[license]: https://github.com/aantron/better-enums/blob/master/doc/LICENSE

doc/ApiReference.md

@@ -228,7 +228,7 @@ If the given string is the exact name of a declared constant, returns the
 constant. Otherwise, throws `std::runtime_error`. Running time is linear in the
 number of declared constants multiplied by the length of the longest constant.
 
-#### static constexpr optional<Enum> <em>_from_string_nothrow</em>(const char*)
+#### static constexpr optional&lt;Enum&gt; <em>_from_string_nothrow</em>(const char*)
 
 Same as [`_from_string`](#_from_string), but does not throw an exception on
 failure. Returns an [optional value](#StructBetter_enumsoptional) instead.
@@ -238,7 +238,7 @@ failure. Returns an [optional value](#StructBetter_enumsoptional) instead.
 Same as [`_from_string`](#_from_string), but comparison is up to case, in the
 usual sense in the Latin-1 encoding.
 
-#### static constexpr optional<Enum> <em>_from_string_nocase_nothrow</em>(const char*)
+#### static constexpr optional&lt;Enum&gt; <em>_from_string_nocase_nothrow</em>(const char*)
 
 Is to [`_from_string_nocase`](#_from_string_nocase) as
 [`_from_string_nothrow`](#_from_string_nothrow) is to
@@ -342,7 +342,7 @@ of one of the declared constants.
     <em>Enum::_from_integral</em>(<em>2</em>);    // Enum::C
     <em>Enum::_from_integral</em>(<em>42</em>);   // std::runtime_error
 
-#### static constexpr optional<Enum> <em>_from_integral_nothrow</em>(_integral)
+#### static constexpr optional&lt;Enum&gt; <em>_from_integral_nothrow</em>(_integral)
 
 Checked conversion as [`_from_integral`](#_from_integral), but does not throw an
 exception on failure. Returns an [optional value](#StructBetter_enumsoptional)
@@ -370,6 +370,34 @@ constants.
 
 
 
+### Index lookup
+
+#### member constexpr std::size_t <em>_to_index</em>() const
+
+Returns the index of a Better Enum value within its enum declaration. The index
+is determined from the value only; if two constants in the declaration have the
+same value, this function may return the index of either constant.
+
+If the value does not correspond to any constant in the declaration (for
+example, if it was obtained using an unchecked conversion or a cast), then the
+behavior of `value._to_index` is undefined.
+
+#### static constexpr Enum <em>_from_index</em>(size_t)
+
+Returns the value of the constant with the given index. Throws
+`std::runtime_error` if not given the index of one of the constants.
+
+#### static constexpr Enum <em>_from_index_unchecked</em>(size_t)
+
+Returns the value of the constant with the given index. If not given one of the
+constants in the declaration of the enum, the returned value is undefined.
+
+#### static constexpr optional&lt;Enum&gt; <em>_from_index_nothrow</em>(size_t)
+
+Returns the value of the constant with the given index.
+
+
+
 ### Stream operators
 
 #### non-member std::ostream& <em>operator <<</em>(std::ostream&, const Enum&)
@@ -385,6 +413,21 @@ as [`_from_string`](#_from_string). In case of failure, sets the stream's
 
 
 
+### Hashing
+
+#### macro <em>BETTER_ENUMS_DECLARE_STD_HASH</em>(Enum)
+
+Use this outside namespace scope to declare a specialization of `std::hash` for
+the type `Enum`. For example:
+
+    // This declaration might be inside a namespace.
+    <em>BETTER_ENUM</em>(<em>Channel</em>, int, Red, Green, Blue)
+
+    // Later, outside the namespace:
+    <em>BETTER_ENUMS_DECLARE_STD_HASH</em>(<em>Channel</em>)
+
+
+
 %% class = api
 
 %% description = Detailed description of the Better Enums API.

doc/Contact.md

@@ -1,15 +0,0 @@
-## Contact
-
-- Send me an email: [antonbachin@yahoo.com](mailto:antonbachin@yahoo.com).
-- Visit the [GitHub]($repo) project to open an issue or get a development
-  version.
-
-I'm happy to hear any feedback. If you have any trouble using the library or
-parsing the documentation, please don't hesitate to let me know. I'd also be
-interested to hear about your use case, if you are willing to share :)
-
-And, if you find this library helpful, give it a star on GitHub to let me know
-you use it :)
-
-%% description =
-Contact information for Better Enums bugs, issues, support, and feedback.

doc/LICENSE

@@ -1,68 +0,0 @@
-Better Enums is distributed under the terms of the 2-clause BSD license. Its
-text is given below.
-
-
-Copyright (c) 2012-2019, Anton Bachin
-All rights reserved.
-
-Redistribution and use in source and binary forms, with or without modification,
-are permitted provided that the following conditions are met:
-
-1. Redistributions of source code must retain the above copyright notice, this
-list of conditions and the following disclaimer.
-
-2. Redistributions in binary form must reproduce the above copyright notice,
-this list of conditions and the following disclaimer in the documentation and/or
-other materials provided with the distribution.
-
-THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
-ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
-WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
-DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
-ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
-(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
-ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
-SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-
-
-
-
-Better Enums uses the mistune library as part of its documentation generator.
-Its web address and license are given below.
-
-
-http://mistune.readthedocs.org/en/latest/
-
-
-Copyright (c) 2014 - 2015, Hsiaoming Yang
-
-All rights reserved.
-
-Redistribution and use in source and binary forms, with or without modification,
-are permitted provided that the following conditions are met:
-
-* Redistributions of source code must retain the above copyright notice, this
-list of conditions and the following disclaimer.
-
-* Redistributions in binary form must reproduce the above copyright notice, this
-list of conditions and the following disclaimer in the documentation and/or
-other materials provided with the distribution.
-
-* Neither the name of the creator nor the names of its contributors may be used
-to endorse or promote products derived from this software without specific prior
-written permission.
-
-
-THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
-ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
-WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
-DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
-ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
-(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
-ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
-SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

doc/OptInFeatures.md

@@ -88,3 +88,15 @@ Here they are:
 
 %% description = Optional Better Enums features, disabled by default for
 performance or compatibility reasons.
+
+### Injecting tokens
+
+You can define `BETTER_ENUMS_CLASS_ATTRIBUTE` before declaring a Better Enum, to
+inject tokens into the class declaration. For example, in
+
+    #define <em>BETTER_ENUMS_CLASS_ATTRIBUTE</em> <em>__attribute__(foo)</em>
+    <em>BETTER_ENUM</em>(<em>Channel</em>, int, Red, Green, Blue)
+
+The resulting enum declaration will begin with
+
+    class <em>__attribute__(foo)</em> <em>Channel</em> {

doc/better-enums.css

@@ -19,7 +19,7 @@ pre {
     background-color: #477093;
     padding: 1.5em 20px;
     border-radius: 5px;
-    overflow: scroll;
+    overflow: auto;
     color: rgba(255, 255, 255, 0.6);
     font-size: 78%;
     max-width: 84ex;

doc/index.md

@@ -69,10 +69,7 @@ It's what built-in enums ought to support. Better Enums simply adds the missing
 features. And, it is based on the best known techniques, thoroughly tested,
 fast, portable, and documented exhaustively.
 
-To use it, just include <code>enum.h</code>.
-
-Try it live online in
-[Wandbox](http://melpon.org/wandbox/permlink/6kFervewqeDsNAGu), or begin the
+To use it, just include <code>enum.h</code> and begin the
 [tutorial](${prefix}tutorial/HelloWorld.html)!
 
 <div class="hack"></div>

doc/template/footer.tmpl

@@ -3,7 +3,7 @@
 
 <footer>
   <div class="container">
-    Copyright &copy; 2015-2019 Anton Bachin. Released under the BSD 2-clause
+    Copyright &copy; 2015-2024 Anton Bachin. Released under the BSD 2-clause
     license. See
     <a href="https://github.com/aantron/better-enums/blob/$ref/doc/LICENSE">
     LICENSE</a>.

doc/template/header.tmpl

@@ -25,7 +25,6 @@ $ga
     <a href="${prefix}index.html">Home</a>
     <a href="${prefix}tutorial/HelloWorld.html">Tutorial</a>
     <a href="${prefix}ApiReference.html">Reference</a>
-    <a href="${prefix}Contact.html">Contact</a>
   </div>
 </nav>
 

doc/template/ref.tmpl

@@ -1 +1 @@
-0.11.2
+0.11.3

doc/template/version.tmpl

@@ -1 +1 @@
-0.11.2
+0.11.3

enum.h

@@ -1,6 +1,7 @@
 // This file is part of Better Enums, released under the BSD 2-clause license.
-// See doc/LICENSE for details, or visit http://github.com/aantron/better-enums.
+// See LICENSE.md for details, or visit http://github.com/aantron/better-enums.
 
+// clang-format off
 #pragma once
 
 #ifndef BETTER_ENUMS_ENUM_H
@@ -14,6 +15,48 @@
 #include <stdexcept>
 
 
+// in-line, non-#pragma warning handling
+// not supported in very old compilers (namely gcc 4.4 or less)
+#ifdef __GNUC__
+#   ifdef __clang__
+#      define BETTER_ENUMS_IGNORE_OLD_CAST_HEADER _Pragma("clang diagnostic push")
+#      define BETTER_ENUMS_IGNORE_OLD_CAST_BEGIN _Pragma("clang diagnostic ignored \"-Wold-style-cast\"")
+#      define BETTER_ENUMS_IGNORE_OLD_CAST_END _Pragma("clang diagnostic pop")
+#      define BETTER_ENUMS_IGNORE_ATTRIBUTES_HEADER
+#      define BETTER_ENUMS_IGNORE_ATTRIBUTES_BEGIN
+#      define BETTER_ENUMS_IGNORE_ATTRIBUTES_END
+#   else
+#      define BETTER_ENUMS_GCC_VERSION (__GNUC__ * 10000 + __GNUC_MINOR__ * 100)
+#      if BETTER_ENUMS_GCC_VERSION > 40400
+#         define BETTER_ENUMS_IGNORE_OLD_CAST_HEADER _Pragma("GCC diagnostic push")
+#         define BETTER_ENUMS_IGNORE_OLD_CAST_BEGIN _Pragma("GCC diagnostic ignored \"-Wold-style-cast\"")
+#         define BETTER_ENUMS_IGNORE_OLD_CAST_END _Pragma("GCC diagnostic pop")
+#         if (BETTER_ENUMS_GCC_VERSION >= 70300)
+#               define BETTER_ENUMS_IGNORE_ATTRIBUTES_HEADER _Pragma("GCC diagnostic push")
+#               define BETTER_ENUMS_IGNORE_ATTRIBUTES_BEGIN _Pragma("GCC diagnostic ignored \"-Wattributes\"")
+#               define BETTER_ENUMS_IGNORE_ATTRIBUTES_END _Pragma("GCC diagnostic pop")
+#         else
+#               define BETTER_ENUMS_IGNORE_ATTRIBUTES_HEADER
+#               define BETTER_ENUMS_IGNORE_ATTRIBUTES_BEGIN
+#               define BETTER_ENUMS_IGNORE_ATTRIBUTES_END
+#         endif
+#      else
+#         define BETTER_ENUMS_IGNORE_OLD_CAST_HEADER
+#         define BETTER_ENUMS_IGNORE_OLD_CAST_BEGIN
+#         define BETTER_ENUMS_IGNORE_OLD_CAST_END
+#         define BETTER_ENUMS_IGNORE_ATTRIBUTES_HEADER
+#         define BETTER_ENUMS_IGNORE_ATTRIBUTES_BEGIN
+#         define BETTER_ENUMS_IGNORE_ATTRIBUTES_END
+#      endif
+#   endif
+#else // empty definitions for compilers that don't support _Pragma
+#   define BETTER_ENUMS_IGNORE_OLD_CAST_HEADER
+#   define BETTER_ENUMS_IGNORE_OLD_CAST_BEGIN
+#   define BETTER_ENUMS_IGNORE_OLD_CAST_END
+#   define BETTER_ENUMS_IGNORE_ATTRIBUTES_HEADER
+#   define BETTER_ENUMS_IGNORE_ATTRIBUTES_BEGIN
+#   define BETTER_ENUMS_IGNORE_ATTRIBUTES_END
+#endif
 
 // Feature detection.
 
@@ -364,6 +407,8 @@ continue_with(T, U value) { return value; }
 
 // Values array declaration helper.
 
+//! Get intrinsic value of an (Enum::value) by taking advantage of
+// C-conversion's parentheses priority
 template <typename EnumType>
 struct _eat_assign {
     explicit BETTER_ENUMS_CONSTEXPR_ _eat_assign(EnumType value) : _value(value)
@@ -583,6 +628,10 @@ constexpr const char    *_final_ ## index =                                    \
 
 #endif
 
+#ifndef BETTER_ENUMS_CLASS_ATTRIBUTE
+#   define BETTER_ENUMS_CLASS_ATTRIBUTE
+#endif
+
 #define BETTER_ENUMS_TYPE(SetUnderlyingType, SwitchType, GenerateSwitchType,   \
                           GenerateStrings, ToStringConstexpr,                  \
                           DeclareInitialize, DefineInitialize, CallInitialize, \
@@ -594,7 +643,7 @@ BETTER_ENUMS_ID(GenerateSwitchType(Underlying, __VA_ARGS__))                   \
                                                                                \
 }                                                                              \
                                                                                \
-class Enum {                                                                   \
+class BETTER_ENUMS_CLASS_ATTRIBUTE Enum {                                      \
   private:                                                                     \
     typedef ::better_enums::optional<Enum>                  _optional;         \
     typedef ::better_enums::optional<std::size_t>           _optional_index;   \
@@ -624,12 +673,12 @@ class Enum {                                                                   \
                                                                                \
     BETTER_ENUMS_CONSTEXPR_ std::size_t _to_index() const;                     \
     BETTER_ENUMS_IF_EXCEPTIONS(                                                \
-    BETTER_ENUMS_CONSTEXPR_ static Enum _from_index(std::size_t value);        \
+    BETTER_ENUMS_CONSTEXPR_ static Enum _from_index(std::size_t index);        \
     )                                                                          \
     BETTER_ENUMS_CONSTEXPR_ static Enum                                        \
-    _from_index_unchecked(std::size_t value);                                  \
+    _from_index_unchecked(std::size_t index);                                  \
     BETTER_ENUMS_CONSTEXPR_ static _optional                                   \
-    _from_index_nothrow(std::size_t value);                                    \
+    _from_index_nothrow(std::size_t index);                                    \
                                                                                \
     ToStringConstexpr const char* _to_string() const;                          \
     BETTER_ENUMS_IF_EXCEPTIONS(                                                \
@@ -690,19 +739,25 @@ static ::better_enums::_initialize_at_program_start<Enum>                      \
                                                                                \
 enum _putNamesInThisScopeAlso { __VA_ARGS__ };                                 \
                                                                                \
+BETTER_ENUMS_IGNORE_OLD_CAST_HEADER                                            \
+BETTER_ENUMS_IGNORE_OLD_CAST_BEGIN                                             \
 BETTER_ENUMS_CONSTEXPR_ const Enum      _value_array[] =                       \
     { BETTER_ENUMS_ID(BETTER_ENUMS_EAT_ASSIGN(Enum, __VA_ARGS__)) };           \
+BETTER_ENUMS_IGNORE_OLD_CAST_END                                               \
                                                                                \
 BETTER_ENUMS_ID(GenerateStrings(Enum, __VA_ARGS__))                            \
                                                                                \
 }                                                                              \
                                                                                \
+BETTER_ENUMS_IGNORE_ATTRIBUTES_HEADER                                          \
+BETTER_ENUMS_IGNORE_ATTRIBUTES_BEGIN                                           \
 BETTER_ENUMS_UNUSED BETTER_ENUMS_CONSTEXPR_                                    \
 inline const Enum                                                              \
 operator +(Enum::_enumerated enumerated)                                       \
 {                                                                              \
     return static_cast<Enum>(enumerated);                                      \
 }                                                                              \
+BETTER_ENUMS_IGNORE_ATTRIBUTES_END                                             \
                                                                                \
 BETTER_ENUMS_CONSTEXPR_ inline Enum::_optional_index                           \
 Enum::_from_value_loop(Enum::_integral value, std::size_t index)               \
@@ -873,6 +928,8 @@ ToStringConstexpr inline Enum::_name_iterable Enum::_names()                   \
                                                                                \
 DefineInitialize(Enum)                                                         \
                                                                                \
+BETTER_ENUMS_IGNORE_ATTRIBUTES_HEADER                                          \
+BETTER_ENUMS_IGNORE_ATTRIBUTES_BEGIN                                           \
 BETTER_ENUMS_UNUSED BETTER_ENUMS_CONSTEXPR_                                    \
 inline bool operator ==(const Enum &a, const Enum &b)                          \
     { return a._to_integral() == b._to_integral(); }                           \
@@ -896,6 +953,7 @@ inline bool operator >(const Enum &a, const Enum &b)                           \
 BETTER_ENUMS_UNUSED BETTER_ENUMS_CONSTEXPR_                                    \
 inline bool operator >=(const Enum &a, const Enum &b)                          \
     { return a._to_integral() >= b._to_integral(); }                           \
+BETTER_ENUMS_IGNORE_ATTRIBUTES_END                                             \
                                                                                \
                                                                                \
 template <typename Char, typename Traits>                                      \
@@ -1255,4 +1313,16 @@ BETTER_ENUMS_CONSTEXPR_ map<Enum, T> make_map(T (*f)(Enum))
 
 }
 
+#define BETTER_ENUMS_DECLARE_STD_HASH(type)                                    \
+    namespace std {                                                            \
+    template <> struct hash<type>                                              \
+    {                                                                          \
+        size_t operator()(const type &x) const                                 \
+        {                                                                      \
+            return std::hash<size_t>()(x._to_integral());                      \
+        }                                                                      \
+    };                                                                         \
+    }
+
 #endif // #ifndef BETTER_ENUMS_ENUM_H
+// clang-format on

test/cxxtest/general.h

@@ -31,7 +31,10 @@ BETTER_ENUM(Namespaced, short, One, Two)
 // be changed to be more precise in the future.
 #ifdef BETTER_ENUMS_HAVE_CONSTEXPR_
 
+BETTER_ENUMS_DECLARE_STD_HASH(Channel)
+
 #include <type_traits>
+#include <functional>
 
 // Type properties.
 static_assert_1(std::is_class<Channel>());
@@ -161,6 +164,24 @@ static_assert_1(same_string(Depth::_names()[0], "HighColor"));
 
 
 // Run-time testing.
+class HashTests : public CxxTest::TestSuite {
+  public:
+    void test_same_values()
+    {
+#ifdef _ENUM_HAVE_CONSTEXPR
+        TS_ASSERT_EQUALS(
+            std::hash<Channel>().operator()(Channel::Red),
+            std::hash<int>().operator()(0));
+        TS_ASSERT_EQUALS(
+            std::hash<Channel>().operator()(Channel::Green),
+            std::hash<int>().operator()(1));
+        TS_ASSERT_EQUALS(
+            std::hash<Channel>().operator()(Channel::Blue),
+            std::hash<int>().operator()(2));
+#endif // #ifdef _ENUM_HAVE_CONSTEXPR
+    }
+};
+
 class EnumTests : public CxxTest::TestSuite {
   public:
     void test_constant_values()