From 75940488506df9560dd71ea86448a2e271f02c79 Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Wed, 23 Aug 2023 11:42:43 +0200
Subject: [PATCH] fix: `relative_point_origin::quantity_spec` setting fixed

---
 src/core/include/mp-units/quantity_point.h    | 13 +++++++++----
 test/unit_test/static/quantity_point_test.cpp | 17 +++++++++++++++++
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/src/core/include/mp-units/quantity_point.h b/src/core/include/mp-units/quantity_point.h
index c3bfa6df..67d96037 100644
--- a/src/core/include/mp-units/quantity_point.h
+++ b/src/core/include/mp-units/quantity_point.h
@@ -29,16 +29,21 @@
 
 namespace mp_units {
 
-template<QuantitySpec auto Q>
+template<QuantitySpec auto QS>
 struct absolute_point_origin {
-  static constexpr QuantitySpec auto quantity_spec = Q;
+  static constexpr QuantitySpec auto quantity_spec = QS;
 };
 
 template<QuantityPoint auto QP>
 struct relative_point_origin {
   static constexpr QuantityPoint auto quantity_point = QP;
-  static constexpr QuantitySpec auto quantity_spec =
-    common_quantity_spec(QP.quantity_spec, QP.point_origin.quantity_spec);
+  static constexpr QuantitySpec auto quantity_spec = [](){
+    // select the strongest of specs
+    if constexpr (detail::QuantityKindSpec<std::remove_const_t<decltype(QP.quantity_spec)>>)
+      return QP.point_origin.quantity_spec;
+    else
+      return QP.quantity_spec;
+  }();
   static constexpr PointOrigin auto absolute_point_origin = QP.absolute_point_origin;
 };
 
diff --git a/test/unit_test/static/quantity_point_test.cpp b/test/unit_test/static/quantity_point_test.cpp
index 272aedc0..3b7a320f 100644
--- a/test/unit_test/static/quantity_point_test.cpp
+++ b/test/unit_test/static/quantity_point_test.cpp
@@ -1156,5 +1156,22 @@ static_assert(invalid_addition(5 * activity[Bq], 10 / (2 * isq::time[s]), zero_H
 static_assert(invalid_subtraction(zero_Bq + 5 * activity[Bq], 10 / (2 * isq::time[s]), 5 * isq::frequency[Hz]));
 
 
+/////////////////////////
+// relative point origin
+/////////////////////////
+
+template<auto QS>
+struct absolute_po_ : absolute_point_origin<QS> {};
+template<auto QS>
+inline constexpr absolute_po_<QS> absolute_po;
+
+template<auto QP>
+struct relative_po_ : relative_point_origin<QP> {};
+template<auto QP>
+inline constexpr relative_po_<QP> relative_po;
+
+static_assert(relative_po<absolute_po<isq::length> + isq::height(42 * m)>.quantity_spec == isq::height);
+static_assert(relative_po<absolute_po<kind_of<isq::length>> + isq::height(42 * m)>.quantity_spec == isq::height);
+static_assert(relative_po<absolute_po<isq::height> + 42 * m>.quantity_spec == isq::height);
 
 }  // namespace