From 0caf998df13c3bde5fd2ca8cc10bb50f978a25bb Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Thu, 22 Dec 2022 21:28:49 +0100
Subject: [PATCH] refactor: `reference::operator()` return type constraints
 improved

---
 src/core/include/units/reference.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/core/include/units/reference.h b/src/core/include/units/reference.h
index e8987a32..626d7524 100644
--- a/src/core/include/units/reference.h
+++ b/src/core/include/units/reference.h
@@ -53,7 +53,7 @@ struct reference {
 
   template<RepresentationOf<Q.character> Rep>
   // TODO can we somehow return an explicit quantity type here?
-  [[nodiscard]] constexpr Quantity auto operator()(Rep&& value) const
+  [[nodiscard]] constexpr std::same_as<quantity<reference{}, Rep>> auto operator()(Rep&& value) const
   {
     return quantity<reference{}, Rep>(std::forward<Rep>(value));
   }