From d4278494777abc712e897aed9aab8d799fbcbe94 Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Wed, 27 Sep 2023 17:10:20 +0200
Subject: [PATCH] refactor: `in(U)` and `force_in(U)` now return `auto` to
 provide better diagnostics on clang

When a strong type was returned clang, instead of on a concept check, failed on `detail::make_quantity` used to provide a function return type.
---
 src/core/include/mp-units/quantity.h       | 4 ++--
 src/core/include/mp-units/quantity_point.h | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/core/include/mp-units/quantity.h b/src/core/include/mp-units/quantity.h
index 498a9a32..23a1f6c3 100644
--- a/src/core/include/mp-units/quantity.h
+++ b/src/core/include/mp-units/quantity.h
@@ -144,14 +144,14 @@ public:
   // conversions
   template<UnitCompatibleWith<unit, quantity_spec> U>
     requires detail::QuantityConvertibleTo<quantity, quantity<detail::make_reference(quantity_spec, U{}), Rep>>
-  [[nodiscard]] constexpr quantity<detail::make_reference(quantity_spec, U{}), Rep> in(U) const
+  [[nodiscard]] constexpr Quantity auto in(U) const
   {
     return quantity<detail::make_reference(quantity_spec, U{}), Rep>{*this};
   }
 
   template<UnitCompatibleWith<unit, quantity_spec> U>
     requires requires(quantity q) { value_cast<U{}>(q); }
-  [[nodiscard]] constexpr quantity<detail::make_reference(quantity_spec, U{}), Rep> force_in(U) const
+  [[nodiscard]] constexpr Quantity auto force_in(U) const
   {
     return value_cast<U{}>(*this);
   }
diff --git a/src/core/include/mp-units/quantity_point.h b/src/core/include/mp-units/quantity_point.h
index 74a51d92..3e158770 100644
--- a/src/core/include/mp-units/quantity_point.h
+++ b/src/core/include/mp-units/quantity_point.h
@@ -170,14 +170,14 @@ public:
 
   template<UnitCompatibleWith<unit, quantity_spec> U>
     requires detail::QuantityConvertibleTo<quantity_type, quantity<detail::make_reference(quantity_spec, U{}), Rep>>
-  [[nodiscard]] constexpr quantity_point<detail::make_reference(quantity_spec, U{}), PO, Rep> in(U) const
+  [[nodiscard]] constexpr QuantityPoint auto in(U) const
   {
     return make_quantity_point<PO>(quantity_ref_from(PO).in(U{}));
   }
 
   template<UnitCompatibleWith<unit, quantity_spec> U>
     requires requires(quantity_type q) { value_cast<U{}>(q); }
-  [[nodiscard]] constexpr quantity_point<detail::make_reference(quantity_spec, U{}), PO, Rep> force_in(U) const
+  [[nodiscard]] constexpr QuantityPoint auto force_in(U) const
   {
     return make_quantity_point<PO>(quantity_ref_from(PO).force_in(U{}));
   }