From 6364fcdf7ee53a0e28d4a4dba54ac779c366cc5f Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Mon, 5 Jun 2023 19:26:53 +0200
Subject: [PATCH] fix: `IntermediateDerivedQuantitySpec` now also accounts for
 `kind_of`

---
 .../include/mp-units/bits/quantity_spec_concepts.h  |  5 ++++-
 test/unit_test/static/quantity_spec_test.cpp        | 13 +++++++++++--
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/core/include/mp-units/bits/quantity_spec_concepts.h b/src/core/include/mp-units/bits/quantity_spec_concepts.h
index 1b5afa2a..27543dde 100644
--- a/src/core/include/mp-units/bits/quantity_spec_concepts.h
+++ b/src/core/include/mp-units/bits/quantity_spec_concepts.h
@@ -131,7 +131,10 @@ namespace detail {
  * explicitly not supported here.
  */
 template<typename T>
-concept IntermediateDerivedQuantitySpec = is_specialization_of<T, derived_quantity_spec>;
+concept IntermediateDerivedQuantitySpec =
+  is_specialization_of<T, derived_quantity_spec> ||
+  (QuantityKindSpec<T> &&
+   is_specialization_of<std::remove_const_t<decltype(T::_quantity_spec_)>, derived_quantity_spec>);
 
 }  // namespace detail
 
diff --git a/test/unit_test/static/quantity_spec_test.cpp b/test/unit_test/static/quantity_spec_test.cpp
index a48db799..5ed6c059 100644
--- a/test/unit_test/static/quantity_spec_test.cpp
+++ b/test/unit_test/static/quantity_spec_test.cpp
@@ -128,16 +128,22 @@ static_assert(!detail::NamedQuantitySpec<decltype(1 / time)>);
 static_assert(detail::IntermediateDerivedQuantitySpec<decltype(1 / time)>);
 static_assert(!detail::QuantityKindSpec<decltype(1 / time)>);
 
+static_assert(QuantitySpec<kind_of_<length / time>>);
+static_assert(!detail::BaseQuantitySpec<kind_of_<length / time>>);
+static_assert(!detail::NamedQuantitySpec<kind_of_<length / time>>);
+static_assert(detail::IntermediateDerivedQuantitySpec<kind_of_<length / time>>);
+static_assert(detail::QuantityKindSpec<kind_of_<length / time>>);
+
 static_assert(QuantitySpec<decltype(kind_of<length> / kind_of<time>)>);
 static_assert(!detail::BaseQuantitySpec<decltype(kind_of<length> / kind_of<time>)>);
 static_assert(!detail::NamedQuantitySpec<decltype(kind_of<length> / kind_of<time>)>);
-static_assert(!detail::IntermediateDerivedQuantitySpec<decltype(kind_of<length> / kind_of<time>)>);
+static_assert(detail::IntermediateDerivedQuantitySpec<decltype(kind_of<length> / kind_of<time>)>);
 static_assert(detail::QuantityKindSpec<decltype(kind_of<length> / kind_of<time>)>);
 
 static_assert(QuantitySpec<decltype(kind_of<length> * kind_of<time>)>);
 static_assert(!detail::BaseQuantitySpec<decltype(kind_of<length> * kind_of<time>)>);
 static_assert(!detail::NamedQuantitySpec<decltype(kind_of<length> * kind_of<time>)>);
-static_assert(!detail::IntermediateDerivedQuantitySpec<decltype(kind_of<length> * kind_of<time>)>);
+static_assert(detail::IntermediateDerivedQuantitySpec<decltype(kind_of<length> * kind_of<time>)>);
 static_assert(detail::QuantityKindSpec<decltype(kind_of<length> * kind_of<time>)>);
 
 // dimensionless
@@ -270,6 +276,9 @@ static_assert(is_of_type<acceleration * mass, derived_quantity_spec<acceleration
 static_assert(is_of_type<(acceleration * mass).dimension,
                          derived_dimension<dim_length_, dim_mass_, per<mp_units::power<dim_time_, 2>>>>);
 
+static_assert(is_of_type<kind_of<length> / kind_of<time>, kind_of_<derived_quantity_spec<length_, per<time_>>{}>>);
+static_assert(is_of_type<kind_of<length / time>, kind_of_<derived_quantity_spec<length_, per<time_>>{}>>);
+
 // power
 static_assert(is_of_type<pow<2>(length), derived_quantity_spec<mp_units::power<length_, 2>>>);
 static_assert(is_of_type<pow<1, 2>(length), derived_quantity_spec<mp_units::power<length_, 1, 2>>>);