add: example of how to use template_string_literal

Author: ObiWahn

include/ext/util/template_string_literal.hpp

@@ -6,7 +6,14 @@
 
 namespace ext::util {
 
+// Usage:
+// template<template_string_literal lit>
+// struct example_class {
+//     const std::string name  = lit.value;
+// };
+
 // c++20 -- class types in non-type template parameters
+// https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0732r2.pdf
 template<std::size_t N>
 struct template_string_literal {
     constexpr template_string_literal(const char (&str)[N]) {

tests/CMakeLists.txt

@@ -39,6 +39,7 @@ set(test-files
     "util_serialization"
     "util_show"
     "util_string"
+    "util_template_string_literal"
     "util_tuple"
     "util_windows_strings"
 )

tests/util_template_string_literal.cpp

@@ -0,0 +1,17 @@
+// Copyright - 2020 - Jan Christoph Uhde <Jan@UhdeJC.com>
+// Please see LICENSE.md for license or visit https://github.com/extcpp/basics
+#include <gtest/gtest.h>
+
+#include <ext/util/template_string_literal.hpp>
+
+using namespace ext::util;
+
+template<template_string_literal lit>
+struct example_class {
+    const std::string name  = lit.value;
+};
+
+TEST(util_template_string_literal, error_to_string) {
+    example_class<"foo"> actual;
+    ASSERT_EQ(actual.name, "foo");
+}