Make constructor from arguments (one without std::in_place) non-`ex…

…plicit`

include/opt/option.hpp

@@ -2851,7 +2851,7 @@ class OPTION_DECLSPEC_EMPTY_BASES OPTION_CONSUMABLE(unconsumed) option
     template<class First, class Second, class... Args,
         class = typename checks::template from_args_ctor<T, First, Second, Args...>::type>
     OPTION_RETURN_TYPESTATE(consumed)
-    constexpr explicit option(First&& first, Second&& second, Args&&... args)
+    constexpr option(First&& first, Second&& second, Args&&... args)
         : base(std::in_place, std::bool_constant<std::is_aggregate_v<T>>{}, static_cast<First&&>(first), static_cast<Second&&>(second), static_cast<Args&&>(args)...) {}
 
     template<class InPlaceT, class... Args,

test/special.test.cpp

@@ -1740,6 +1740,28 @@ TEST_CASE("value_or") {
 #endif
 }
 
+TEST_CASE("non-explicit from arguments constructor") {
+    struct type {
+        int x;
+        float y;
+
+        bool operator==(const type& other) const { return x == other.x && y == other.y; }
+    };
+    const auto fn1 = []() -> type {
+        return {1, 2.f};
+    };
+    CHECK_EQ(fn1(), type{1, 2.f});
+    const auto fn2 = []() -> opt::option<type> {
+        return {3, 4.f};
+    };
+    CHECK_EQ(fn2(), type{3, 4.f});
+
+    const auto fn3 = [](type) {};
+    fn3({5, 6.f});
+    const auto fn4 = [](opt::option<type>) {};
+    fn4({7, 8.f});
+}
+
 TEST_SUITE_END();
 
 struct struct1 {