src: Add inequality operator for StringRef

src/template.h

@@ -342,6 +342,22 @@ inline bool operator==(const char *lhs, const StringRef &rhs) {
   return rhs == lhs;
 }
 
+inline bool operator!=(const StringRef &lhs, const std::string &rhs) {
+  return !(lhs == rhs);
+}
+
+inline bool operator!=(const std::string &lhs, const StringRef &rhs) {
+  return !(rhs == lhs);
+}
+
+inline bool operator!=(const StringRef &lhs, const char *rhs) {
+  return !(lhs == rhs);
+}
+
+inline bool operator!=(const char *lhs, const StringRef &rhs) {
+  return !(rhs == lhs);
+}
+
 inline int run_app(std::function<int(int, char **)> app, int argc,
                    char **argv) {
   try {

src/template_test.cc

@@ -87,6 +87,14 @@ void test_template_immutable_string(void) {
 
   CU_ASSERT("bravo" == from_lit);
   CU_ASSERT(5 == from_lit.size());
+
+  // equality
+  ImmutableString eq("delta");
+
+  CU_ASSERT("delta1" != eq);
+  CU_ASSERT("delt" != eq);
+  CU_ASSERT(eq != "delta1");
+  CU_ASSERT(eq != "delt");
 }
 
 void test_template_string_ref(void) {