feat: add meet_expected

remove expected_or<>()

include/rua/error.hpp

@@ -206,6 +206,10 @@ inline error_i current_exception_error() {
 
 RUA_CVAR strv_error unexpected("unexpected");
 
+struct meet_expected_t {};
+
+RUA_CVAL meet_expected_t meet_expected;
+
 template <typename T = void>
 class expected : public enable_value_operators<expected<T>, T> {
 public:
@@ -220,6 +224,8 @@ class expected : public enable_value_operators<expected<T>, T> {
 	expected(std::initializer_list<U> il, Args &&...args) :
 		$v(in_place_type_t<T>{}, il, std::forward<Args>(args)...) {}
 
+	expected(meet_expected_t) : $v(in_place_type_t<T>{}) {}
+
 	expected(const expected &src) : $v(src.$v) {}
 
 	expected(expected &&src) : $v(std::move(src.$v)) {}
@@ -343,6 +349,8 @@ class expected<void> {
 		assert(r);
 	}
 
+	expected(meet_expected_t) : $err() {}
+
 	expected(const expected &src) : $err(src.$err) {}
 
 	expected(expected &&src) : $err(std::move(src.$err)) {}
@@ -391,18 +399,6 @@ class expected<void> {
 
 ////////////////////////////////////////////////////////////////////////////
 
-template <typename T>
-inline expected<T> expected_or(error_i unexpected_err) {
-	return unexpected_err;
-}
-
-template <>
-inline expected<void> expected_or(error_i) {
-	return {};
-}
-
-////////////////////////////////////////////////////////////////////////////
-
 template <typename T>
 struct is_expected : std::false_type {};
 

include/rua/sync/promise.hpp

@@ -51,7 +51,7 @@ class promise<T, void> {
 	//////////////////// fulfill ////////////////////
 
 	void fulfill(
-		expected<T> value = expected_or<T>(err_promise_unfulfilled),
+		expected<T> value = meet_expected,
 		std::function<void(expected<T>)> on_unharvested = nullptr) noexcept {
 
 		assert(std::is_void<T>::value || !$val);