Add errors::nil Function

include/errors/error.hpp

@@ -18,12 +18,6 @@ class Error {
   Error(const std::shared_ptr<const std::string>& message_ptr);
 
  public:
-
-  /**
-   * @brief Constructs an empty error object.
-   */
-  Error();
-
   /**
    * @brief Returns the error message.
    *
@@ -54,6 +48,7 @@ class Error {
   explicit operator bool() const;
 
   friend Error make(const std::string& msg);
+  friend const Error& nil();
 
   /**
    * @brief Writes the string representation of an error object to the given
@@ -83,4 +78,11 @@ class Error {
  */
 Error make(const std::string& msg);
 
+
+/**
+ * @brief Gets a constant reference of an empty error.
+ * @return A constant reference of an empty error.
+ */
+const Error& nil();
+
 }  // namespace error

src/error.cpp

@@ -4,8 +4,6 @@ namespace errors {
 
 Error::Error(const std::shared_ptr<const std::string>& message_ptr) : message_ptr(message_ptr) {}
 
-Error::Error() {}
-
 std::string_view Error::message() const {
   if (!message_ptr) return "no error";
   return *message_ptr;
@@ -23,4 +21,9 @@ Error make(const std::string& msg) {
   return Error(std::make_shared<const std::string>(msg));
 }
 
+const Error& nil() {
+  static const Error err(nullptr);
+  return err;
+}
+
 }  // namespace error

test/error_test.cpp

@@ -9,7 +9,7 @@ TEST_CASE("Error Construction") {
 }
 
 TEST_CASE("Empty Error Construction") {
-  const errors::Error err;
+  const auto err = errors::nil();
   REQUIRE_FALSE(err);
   REQUIRE(err.message() == "no error");
 }