utils: Improve Mu::Result

Ensure the Ok() and Err() actually work, and add support for Result<void>

lib/utils/mu-result.hh

@@ -25,24 +25,56 @@
 
 namespace Mu {
 /**
- * A Result is _either_ some value of type T, _or_ an error.
+ * A little Rust-envy...a Result is _either_ some value of type T, _or_ a Mu::Error
  */
 template <typename T> using Result = tl::expected<T, Error>;
 
+/**
+ * Ok() is not typically strictly needed (unlike Err), but imitates Rust's Ok
+ * and it helps the reader.
+ *
+ * @param t the value to return
+ *
+ * @return a success Result<T>
+ */
 template <typename T>
-typename Result<T>::expected_type
+typename Result<T>::expected
 Ok(T&& t)
 {
-	return Result<T>::expected(std::move(t));
+	return std::move(t);
 }
 
-template <typename T>
-typename Result<T>::unexpected_type
+/**
+ * Implementation of Ok() for void results.
+ *
+ * @return a success Result<void>
+ */
+static inline Result<void>
+Ok()
+{
+	return {};
+}
+
+/**
+ * Return an error
+ *
+ * @param err the error
+ *
+ * @return error
+ */
+static inline tl::unexpected<Error>
 Err(Error&& err)
 {
-	return Result<T>::unexpected(std::move(err));
+	return tl::unexpected(std::move(err));
+}
+
+static inline tl::unexpected<Error>
+Err(const Error& err)
+{
+	return tl::unexpected(err);
 }
 
 } // namespace Mu
 
-#endif /* MU_ERROR_HH__ */
+
+#endif /* MU_RESULT_HH__ */