Simplify ASSERT_SORT_ORDER

In practice this only looked at the name property, so we can simplify it
by using an ordinary template function instead of a macro.

src/builtin_string.cpp

@@ -1783,7 +1783,7 @@ static constexpr const struct string_subcommand {
     {L"sub", &string_sub},         {L"trim", &string_trim},     {L"unescape", &string_unescape},
     {L"upper", &string_upper},
 };
-ASSERT_SORT_ORDER(string_subcommands, .name);
+ASSERT_SORTED_BY_NAME(string_subcommands);
 
 /// The string builtin, for manipulating strings.
 maybe_t<int> builtin_string(parser_t &parser, io_streams_t &streams, const wchar_t **argv) {

src/color.cpp

@@ -200,7 +200,7 @@ static constexpr named_color_t named_colors[] = {
     {L"purple", 5, {0x80, 0x00, 0x80}, true},      {L"red", 1, {0x80, 0x00, 0x00}, false},
     {L"white", 7, {0xC0, 0xC0, 0xC0}, false},      {L"yellow", 3, {0x80, 0x80, 0x00}, false},
 };
-ASSERT_SORT_ORDER(named_colors, .name);
+ASSERT_SORTED_BY_NAME(named_colors);
 
 wcstring_list_t rgb_color_t::named_color_names() {
     wcstring_list_t result;

src/common.h

@@ -710,20 +710,13 @@ constexpr size_t const_strlen(const T (&val)[N], size_t last_checked_idx = N,
                               val[last_checked_idx - 1] ? first_nul_idx : last_checked_idx - 1);
 }
 
-/// Compile-time assertion of alphabetical sort of array `array`, by specified
-/// parameter `accessor`. This is only a macro because constexpr lambdas (to
-/// specify the accessor for the sort key) are C++17 and up.
-#define ASSERT_SORT_ORDER(array, accessor)                                                \
-    struct verify_##array##_sort_t {                                                      \
-        template <class T, size_t N>                                                      \
-        constexpr static bool validate(T (&vals)[N], size_t idx = 0) {                    \
-            return (idx == (((sizeof(array) / sizeof(vals[0]))) - 1))                     \
-                       ? true                                                             \
-                       : const_strcmp(vals[idx] accessor, vals[idx + 1] accessor) <= 0 && \
-                             verify_##array##_sort_t::validate<T, N>(vals, idx + 1);      \
-        }                                                                                 \
-    };                                                                                    \
-    static_assert(verify_##array##_sort_t::validate(array),                               \
-                  #array " members not in asciibetical order!");
+/// \return true if the array \p vals is sorted by its name property.
+template <typename T, size_t N>
+constexpr bool is_sorted_by_name(const T (&vals)[N], size_t idx = 1) {
+    return idx >= N ? true
+                    : (const_strcmp(vals[idx - 1].name, vals[idx].name) <= 0 &&
+                       is_sorted_by_name(vals, idx + 1));
+}
+#define ASSERT_SORTED_BY_NAME(x) static_assert(is_sorted_by_name(x), #x " not sorted by name")
 
 #endif  // FISH_COMMON_H

src/env.cpp

@@ -107,7 +107,7 @@ static constexpr const electric_var_t electric_variables[] = {
     {L"umask", electric_var_t::fcomputed},
     {L"version", electric_var_t::freadonly},
 };
-ASSERT_SORT_ORDER(electric_variables, .name);
+ASSERT_SORTED_BY_NAME(electric_variables);
 
 const electric_var_t *electric_var_t::for_name(const wchar_t *name) {
     auto begin = std::begin(electric_variables);

src/fish_tests.cpp

@@ -1698,12 +1698,28 @@ static void test_const_strcmp() {
     static_assert(const_strcmp("b", "aa") > 0, "const_strcmp failure");
 }
 
+static void test_is_sorted_by_name() {
+    struct named_t {
+        const wchar_t *name;
+    };
+
+    static constexpr named_t sorted[] = {
+        {L"a"}, {L"aa"}, {L"aaa"}, {L"aaa"}, {L"aaa"}, {L"aazz"}, {L"aazzzz"},
+    };
+    static_assert(is_sorted_by_name(sorted), "is_sorted_by_name failure");
+    static constexpr named_t not_sorted[] = {
+        {L"a"}, {L"aa"}, {L"aaa"}, {L"q"}, {L"aazz"}, {L"aazz"}, {L"aazz"}, {L"aazzzz"},
+    };
+    static_assert(!is_sorted_by_name(not_sorted), "is_sorted_by_name failure");
+}
+
 static void test_utility_functions() {
     say(L"Testing utility functions");
     test_wcsfilecmp();
     test_parse_util_cmdsubst_extent();
     test_const_strlen();
     test_const_strcmp();
+    test_is_sorted_by_name();
 }
 
 // UTF8 tests taken from Alexey Vatchenko's utf8 library. See http://www.bsdua.org/libbsdua.html.

src/input.cpp

@@ -165,7 +165,7 @@ static constexpr const input_function_metadata_t input_function_metadata[] = {
     {L"yank-pop", readline_cmd_t::yank_pop},
 };
 
-ASSERT_SORT_ORDER(input_function_metadata, .name);
+ASSERT_SORTED_BY_NAME(input_function_metadata);
 static_assert(sizeof(input_function_metadata) / sizeof(input_function_metadata[0]) ==
                   input_function_count,
               "input_function_metadata size mismatch with input_common. Did you forget to update "