From 6aa848a4568bf72ffb856544ca4d1f269bd2e7f8 Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Wed, 12 Jun 2024 14:17:32 +0200
Subject: [PATCH] feat: :boom: from now on dimnensions have to be marked as
 `final`

---
 .../framework_basics/design_overview.md       |  4 ++--
 .../framework_basics/text_output.md           | 14 ++++++-------
 .../framework_basics/value_conversions.md     |  6 +++---
 example/currency.cpp                          |  2 +-
 .../include/mp-units/framework/dimension.h    | 21 +++++++++++--------
 .../mp-units/framework/dimension_concepts.h   | 12 +++--------
 .../mp-units/framework/quantity_spec.h        |  6 +++---
 .../include/mp-units/systems/angular/units.h  |  2 +-
 .../mp-units/systems/iec80000/quantities.h    |  2 +-
 .../mp-units/systems/isq/base_quantities.h    | 14 ++++++-------
 test/static/concepts_test.cpp                 |  8 +++----
 test/static/dimension_test.cpp                | 10 ++++-----
 test/static/quantity_spec_test.cpp            |  6 +++---
 test/static/reference_test.cpp                |  6 +++---
 test/static/unit_test.cpp                     |  8 +++----
 15 files changed, 59 insertions(+), 62 deletions(-)

diff --git a/docs/users_guide/framework_basics/design_overview.md b/docs/users_guide/framework_basics/design_overview.md
index 8513ee80..3f557249 100644
--- a/docs/users_guide/framework_basics/design_overview.md
+++ b/docs/users_guide/framework_basics/design_overview.md
@@ -60,8 +60,8 @@ For example:
 the following way:
 
 ```cpp
-inline constexpr struct dim_length : base_dimension<"L"> {} dim_length;
-inline constexpr struct dim_time : base_dimension<"T"> {} dim_time;
+inline constexpr struct dim_length final : base_dimension<"L"> {} dim_length;
+inline constexpr struct dim_time final : base_dimension<"T"> {} dim_time;
 ```
 
 [Derived dimensions](../../appendix/glossary.md#derived-dimension) are implicitly created
diff --git a/docs/users_guide/framework_basics/text_output.md b/docs/users_guide/framework_basics/text_output.md
index 6487640e..cc6c347d 100644
--- a/docs/users_guide/framework_basics/text_output.md
+++ b/docs/users_guide/framework_basics/text_output.md
@@ -33,13 +33,13 @@ and units of derived quantities.
 === "Dimensions"
 
     ```cpp
-    inline constexpr struct dim_length : base_dimension<"L"> {} dim_length;
-    inline constexpr struct dim_mass : base_dimension<"M"> {} dim_mass;
-    inline constexpr struct dim_time : base_dimension<"T"> {} dim_time;
-    inline constexpr struct dim_electric_current : base_dimension<"I"> {} dim_electric_current;
-    inline constexpr struct dim_thermodynamic_temperature : base_dimension<{u8"Θ", "O"}> {} dim_thermodynamic_temperature;
-    inline constexpr struct dim_amount_of_substance : base_dimension<"N"> {} dim_amount_of_substance;
-    inline constexpr struct dim_luminous_intensity : base_dimension<"J"> {} dim_luminous_intensity;
+    inline constexpr struct dim_length final : base_dimension<"L"> {} dim_length;
+    inline constexpr struct dim_mass final : base_dimension<"M"> {} dim_mass;
+    inline constexpr struct dim_time final : base_dimension<"T"> {} dim_time;
+    inline constexpr struct dim_electric_current final : base_dimension<"I"> {} dim_electric_current;
+    inline constexpr struct dim_thermodynamic_temperature final : base_dimension<{u8"Θ", "O"}> {} dim_thermodynamic_temperature;
+    inline constexpr struct dim_amount_of_substance final : base_dimension<"N"> {} dim_amount_of_substance;
+    inline constexpr struct dim_luminous_intensity final : base_dimension<"J"> {} dim_luminous_intensity;
     ```
 
 === "Units"
diff --git a/docs/users_guide/framework_basics/value_conversions.md b/docs/users_guide/framework_basics/value_conversions.md
index ecc6d6c9..c1df3e6f 100644
--- a/docs/users_guide/framework_basics/value_conversions.md
+++ b/docs/users_guide/framework_basics/value_conversions.md
@@ -85,7 +85,7 @@ the `value_cast<U, Rep>(q)` which always returns the most precise result:
 === "C++23"
 
     ```cpp
-    inline constexpr struct dim_currency : base_dimension<"$"> {} dim_currency;
+    inline constexpr struct dim_currency final : base_dimension<"$"> {} dim_currency;
     inline constexpr struct currency : quantity_spec<dim_currency> {} currency;
 
     inline constexpr struct us_dollar final : named_unit<"USD", kind_of<currency>> {} us_dollar;
@@ -105,7 +105,7 @@ the `value_cast<U, Rep>(q)` which always returns the most precise result:
 === "C++20"
 
     ```cpp
-    inline constexpr struct dim_currency : base_dimension<"$"> {} dim_currency;
+    inline constexpr struct dim_currency final : base_dimension<"$"> {} dim_currency;
     inline constexpr struct currency : quantity_spec<currency, dim_currency> {} currency;
 
     inline constexpr struct us_dollar final : named_unit<"USD", kind_of<currency>> {} us_dollar;
@@ -125,7 +125,7 @@ the `value_cast<U, Rep>(q)` which always returns the most precise result:
 === "Portable"
 
     ```cpp
-    inline constexpr struct dim_currency : base_dimension<"$"> {} dim_currency;
+    inline constexpr struct dim_currency final : base_dimension<"$"> {} dim_currency;
     QUANTITY_SPEC(currency, dim_currency);
 
     inline constexpr struct us_dollar final : named_unit<"USD", kind_of<currency>> {} us_dollar;
diff --git a/example/currency.cpp b/example/currency.cpp
index bbbb55cf..b34fdc40 100644
--- a/example/currency.cpp
+++ b/example/currency.cpp
@@ -36,7 +36,7 @@ import mp_units.core;
 using namespace mp_units;
 
 // clang-format off
-inline constexpr struct dim_currency : base_dimension<"$"> {} dim_currency;
+inline constexpr struct dim_currency final : base_dimension<"$"> {} dim_currency;
 
 QUANTITY_SPEC(currency, dim_currency);
 
diff --git a/src/core/include/mp-units/framework/dimension.h b/src/core/include/mp-units/framework/dimension.h
index 63f409de..71d24719 100644
--- a/src/core/include/mp-units/framework/dimension.h
+++ b/src/core/include/mp-units/framework/dimension.h
@@ -62,9 +62,9 @@ namespace mp_units {
  * For example:
  *
  * @code{.cpp}
- * inline constexpr struct dim_length : base_dimension<"L"> {} dim_length;
- * inline constexpr struct dim_time : base_dimension<"T"> {} dim_time;
- * inline constexpr struct dim_mass : base_dimension<"M"> {} dim_mass;
+ * inline constexpr struct dim_length final : base_dimension<"L"> {} dim_length;
+ * inline constexpr struct dim_time final : base_dimension<"T"> {} dim_time;
+ * inline constexpr struct dim_mass final : base_dimension<"M"> {} dim_mass;
  * @endcode
  *
  * @note A common convention in this library is to assign the same name for a type and an object of this type.
@@ -87,6 +87,9 @@ struct base_dimension_less : std::bool_constant<(Lhs::symbol < Rhs::symbol)> {};
 template<typename T1, typename T2>
 using type_list_of_base_dimension_less = expr_less<T1, T2, base_dimension_less>;
 
+template<detail::DerivedDimensionExpr... Expr>
+struct derived_dimension_impl : detail::expr_fractions<detail::is_dimension_one, Expr...> {};
+
 }  // namespace detail
 
 /**
@@ -132,7 +135,7 @@ using type_list_of_base_dimension_less = expr_less<T1, T2, base_dimension_less>;
  *       instantiate this type automatically based on the dimensional arithmetic equation provided by the user.
  */
 template<detail::DerivedDimensionExpr... Expr>
-struct derived_dimension : detail::expr_fractions<detail::is_dimension_one, Expr...> {};
+struct derived_dimension final : detail::derived_dimension_impl<Expr...> {};
 
 /**
  * @brief Dimension one
@@ -141,7 +144,7 @@ struct derived_dimension : detail::expr_fractions<detail::is_dimension_one, Expr
  * dimensions are zero. It is a dimension of a quantity of dimension one also known as
  * "dimensionless".
  */
-MP_UNITS_EXPORT inline constexpr struct dimension_one : derived_dimension<> {
+MP_UNITS_EXPORT inline constexpr struct dimension_one final : detail::derived_dimension_impl<> {
 } dimension_one;
 
 namespace detail {
@@ -280,13 +283,13 @@ constexpr Out dimension_symbol_impl(Out out, const type_list<Nums...>& nums, con
 }
 
 template<typename CharT, std::output_iterator<CharT> Out, typename... Expr>
-constexpr Out dimension_symbol_impl(Out out, const derived_dimension<Expr...>&, const dimension_symbol_formatting& fmt,
-                                    bool negative_power)
+constexpr Out dimension_symbol_impl(Out out, const derived_dimension_impl<Expr...>&,
+                                    const dimension_symbol_formatting& fmt, bool negative_power)
 {
   (void)negative_power;
   MP_UNITS_EXPECTS(negative_power == false);
-  return dimension_symbol_impl<CharT>(out, typename derived_dimension<Expr...>::_num_{},
-                                      typename derived_dimension<Expr...>::_den_{}, fmt);
+  return dimension_symbol_impl<CharT>(out, typename derived_dimension_impl<Expr...>::_num_{},
+                                      typename derived_dimension_impl<Expr...>::_den_{}, fmt);
 }
 
 
diff --git a/src/core/include/mp-units/framework/dimension_concepts.h b/src/core/include/mp-units/framework/dimension_concepts.h
index 11be622d..35913606 100644
--- a/src/core/include/mp-units/framework/dimension_concepts.h
+++ b/src/core/include/mp-units/framework/dimension_concepts.h
@@ -42,20 +42,13 @@ template<typename T>
 inline constexpr bool is_derived_from_specialization_of_base_dimension =
   requires(T* t) { to_base_specialization_of_base_dimension(t); };
 
-template<typename T>
-inline constexpr bool is_specialization_of_base_dimension = false;
-
-template<symbol_text Symbol>
-inline constexpr bool is_specialization_of_base_dimension<base_dimension<Symbol>> = true;
-
 /**
  * @brief A concept matching all named base dimensions in the library.
  *
  * Satisfied by all dimension types derived from a specialization of `base_dimension`.
  */
 template<typename T>
-concept BaseDimension =
-  is_derived_from_specialization_of_base_dimension<T> && (!is_specialization_of_base_dimension<T>);
+concept BaseDimension = is_derived_from_specialization_of_base_dimension<T> && std::is_final_v<T>;
 
 template<typename T>
 struct is_dimension_one : std::false_type {};
@@ -91,7 +84,8 @@ namespace detail {
  * being the `dimension_one`.
  */
 template<typename T>
-concept DerivedDimension = is_specialization_of<T, derived_dimension> || is_dimension_one<T>::value;
+concept DerivedDimension =
+  (is_specialization_of<T, derived_dimension> || is_dimension_one<T>::value) && std::is_final_v<T>;
 
 }  // namespace detail
 
diff --git a/src/core/include/mp-units/framework/quantity_spec.h b/src/core/include/mp-units/framework/quantity_spec.h
index 383a61f3..03098bbc 100644
--- a/src/core/include/mp-units/framework/quantity_spec.h
+++ b/src/core/include/mp-units/framework/quantity_spec.h
@@ -199,9 +199,9 @@ MP_UNITS_EXPORT_END
  * For example:
  *
  * @code{.cpp}
- * inline constexpr struct dim_length : base_dimension<"L"> {} dim_length;
- * inline constexpr struct dim_mass : base_dimension<"M"> {} dim_mass;
- * inline constexpr struct dim_time : base_dimension<"T"> {} dim_time;
+ * inline constexpr struct dim_length final : base_dimension<"L"> {} dim_length;
+ * inline constexpr struct dim_mass final : base_dimension<"M"> {} dim_mass;
+ * inline constexpr struct dim_time final : base_dimension<"T"> {} dim_time;
  *
  * inline constexpr struct length : quantity_spec<dim_length> {} length;
  * inline constexpr struct mass : quantity_spec<dim_mass> {} mass;
diff --git a/src/systems/include/mp-units/systems/angular/units.h b/src/systems/include/mp-units/systems/angular/units.h
index e4747007..45aa42ce 100644
--- a/src/systems/include/mp-units/systems/angular/units.h
+++ b/src/systems/include/mp-units/systems/angular/units.h
@@ -34,7 +34,7 @@ MP_UNITS_EXPORT
 namespace mp_units::angular {
 
 // clang-format off
-inline constexpr struct dim_angle : base_dimension<"A"> {} dim_angle;
+inline constexpr struct dim_angle final : base_dimension<"A"> {} dim_angle;
 QUANTITY_SPEC(angle, dim_angle);
 QUANTITY_SPEC(solid_angle, pow<2>(angle));
 
diff --git a/src/systems/include/mp-units/systems/iec80000/quantities.h b/src/systems/include/mp-units/systems/iec80000/quantities.h
index 04f1191f..f9b23547 100644
--- a/src/systems/include/mp-units/systems/iec80000/quantities.h
+++ b/src/systems/include/mp-units/systems/iec80000/quantities.h
@@ -36,7 +36,7 @@ namespace mp_units::iec80000 {
 
 // dimensions of base quantities
 // clang-format off
-inline constexpr struct dim_traffic_intensity : base_dimension<"A"> {} dim_traffic_intensity;
+inline constexpr struct dim_traffic_intensity final : base_dimension<"A"> {} dim_traffic_intensity;
 // clang-format on
 
 // quantities
diff --git a/src/systems/include/mp-units/systems/isq/base_quantities.h b/src/systems/include/mp-units/systems/isq/base_quantities.h
index 6ed87f7c..c7f4f337 100644
--- a/src/systems/include/mp-units/systems/isq/base_quantities.h
+++ b/src/systems/include/mp-units/systems/isq/base_quantities.h
@@ -35,13 +35,13 @@ namespace mp_units::isq {
 
 // clang-format off
 // dimensions of base quantities
-inline constexpr struct dim_length : base_dimension<"L"> {} dim_length;
-inline constexpr struct dim_mass : base_dimension<"M"> {} dim_mass;
-inline constexpr struct dim_time : base_dimension<"T"> {} dim_time;
-inline constexpr struct dim_electric_current : base_dimension<"I"> {} dim_electric_current;
-inline constexpr struct dim_thermodynamic_temperature : base_dimension<symbol_text{u8"Θ", "O"}> {} dim_thermodynamic_temperature;
-inline constexpr struct dim_amount_of_substance : base_dimension<"N"> {} dim_amount_of_substance;
-inline constexpr struct dim_luminous_intensity : base_dimension<"J"> {} dim_luminous_intensity;
+inline constexpr struct dim_length final : base_dimension<"L"> {} dim_length;
+inline constexpr struct dim_mass final : base_dimension<"M"> {} dim_mass;
+inline constexpr struct dim_time final : base_dimension<"T"> {} dim_time;
+inline constexpr struct dim_electric_current final : base_dimension<"I"> {} dim_electric_current;
+inline constexpr struct dim_thermodynamic_temperature final : base_dimension<symbol_text{u8"Θ", "O"}> {} dim_thermodynamic_temperature;
+inline constexpr struct dim_amount_of_substance final : base_dimension<"N"> {} dim_amount_of_substance;
+inline constexpr struct dim_luminous_intensity final : base_dimension<"J"> {} dim_luminous_intensity;
 // clang-format on
 
 // base quantities
diff --git a/test/static/concepts_test.cpp b/test/static/concepts_test.cpp
index 33fd85a5..df19711f 100644
--- a/test/static/concepts_test.cpp
+++ b/test/static/concepts_test.cpp
@@ -45,7 +45,7 @@ inline constexpr struct my_origin : absolute_point_origin<my_origin, isq::length
 inline constexpr struct my_relative_origin : relative_point_origin<my_origin + isq::length(42 * si::metre)> {
 } my_relative_origin;
 
-struct dim_speed : decltype(isq::dim_length / isq::dim_time) {};
+inline constexpr auto dim_speed = isq::dim_length / isq::dim_time;
 
 // BaseDimension
 static_assert(detail::BaseDimension<struct isq::dim_length>);
@@ -53,7 +53,7 @@ static_assert(!detail::BaseDimension<decltype(isq::dim_length / isq::dim_time)>)
 static_assert(!detail::BaseDimension<decltype(inverse(isq::dim_time))>);
 static_assert(!detail::BaseDimension<decltype(pow<2>(isq::dim_length))>);
 static_assert(!detail::BaseDimension<derived_dimension<struct isq::dim_length, per<struct isq::dim_time>>>);
-static_assert(!detail::BaseDimension<dim_speed>);
+static_assert(!detail::BaseDimension<std::remove_const_t<decltype(dim_speed)>>);
 static_assert(!detail::BaseDimension<base_dimension<"L">>);
 static_assert(!detail::BaseDimension<struct si::metre>);
 static_assert(!detail::BaseDimension<int>);
@@ -64,7 +64,7 @@ static_assert(detail::DerivedDimension<decltype(inverse(isq::dim_time))>);
 static_assert(detail::DerivedDimension<decltype(pow<2>(isq::dim_length))>);
 static_assert(detail::DerivedDimension<derived_dimension<struct isq::dim_length, per<struct isq::dim_time>>>);
 static_assert(detail::DerivedDimension<struct dimension_one>);
-static_assert(!detail::DerivedDimension<dim_speed>);
+static_assert(detail::DerivedDimension<std::remove_const_t<decltype(dim_speed)>>);
 static_assert(!detail::DerivedDimension<struct isq::dim_length>);
 static_assert(!detail::DerivedDimension<struct si::metre>);
 static_assert(!detail::DerivedDimension<int>);
@@ -76,7 +76,7 @@ static_assert(Dimension<decltype(inverse(isq::dim_time))>);
 static_assert(Dimension<decltype(pow<2>(isq::dim_length))>);
 static_assert(Dimension<derived_dimension<struct isq::dim_length, per<struct isq::dim_time>>>);
 static_assert(Dimension<struct dimension_one>);
-static_assert(!Dimension<dim_speed>);
+static_assert(Dimension<std::remove_const_t<decltype(dim_speed)>>);
 static_assert(!Dimension<base_dimension<"L">>);
 static_assert(!Dimension<struct si::metre>);
 static_assert(!Dimension<int>);
diff --git a/test/static/dimension_test.cpp b/test/static/dimension_test.cpp
index a6f0fb36..dc69eab7 100644
--- a/test/static/dimension_test.cpp
+++ b/test/static/dimension_test.cpp
@@ -32,12 +32,12 @@ using namespace mp_units;
 using dimension_one_ = struct dimension_one;
 
 // clang-format off
-inline constexpr struct length_ : base_dimension<"L"> {} length;
-inline constexpr struct mass_ : base_dimension<"M"> {} mass;
-inline constexpr struct time_ : base_dimension<"T"> {} time;
+inline constexpr struct length_ final : base_dimension<"L"> {} length;
+inline constexpr struct mass_ final : base_dimension<"M"> {} mass;
+inline constexpr struct time_ final : base_dimension<"T"> {} time;
 
-inline constexpr struct my_length1_ : decltype(length) {} my_length1;
-inline constexpr struct my_length2_ : decltype(length) {} my_length2;
+inline constexpr auto my_length1 = length;
+inline constexpr auto my_length2 = length;
 
 QUANTITY_SPEC_(q_time, time);
 inline constexpr struct second_ final : named_unit<"s", kind_of<q_time>> {} second;
diff --git a/test/static/quantity_spec_test.cpp b/test/static/quantity_spec_test.cpp
index a2dbd836..7395b6a2 100644
--- a/test/static/quantity_spec_test.cpp
+++ b/test/static/quantity_spec_test.cpp
@@ -33,9 +33,9 @@ using dimensionless_ = struct dimensionless;
 using dim_one_ = struct dimension_one;
 
 // clang-format off
-inline constexpr struct dim_length_ : base_dimension<"L"> {} dim_length;
-inline constexpr struct dim_mass_ : base_dimension<"M"> {} dim_mass;
-inline constexpr struct dim_time_ : base_dimension<"T"> {} dim_time;
+inline constexpr struct dim_length_ final : base_dimension<"L"> {} dim_length;
+inline constexpr struct dim_mass_ final : base_dimension<"M"> {} dim_mass;
+inline constexpr struct dim_time_ final : base_dimension<"T"> {} dim_time;
 
 // quantities specification
 QUANTITY_SPEC_(length, dim_length);
diff --git a/test/static/reference_test.cpp b/test/static/reference_test.cpp
index 5c040d06..e5f6e3be 100644
--- a/test/static/reference_test.cpp
+++ b/test/static/reference_test.cpp
@@ -35,9 +35,9 @@ using one_ = struct one;
 
 // base dimensions
 // clang-format off
-inline constexpr struct dim_length_ : base_dimension<"L"> {} dim_length;
-inline constexpr struct dim_mass_ : base_dimension<"M"> {} dim_mass;
-inline constexpr struct dim_time_ : base_dimension<"T"> {} dim_time;
+inline constexpr struct dim_length_ final : base_dimension<"L"> {} dim_length;
+inline constexpr struct dim_mass_ final : base_dimension<"M"> {} dim_mass;
+inline constexpr struct dim_time_ final : base_dimension<"T"> {} dim_time;
 
 // quantities specification
 QUANTITY_SPEC_(length, dim_length);
diff --git a/test/static/unit_test.cpp b/test/static/unit_test.cpp
index bc39be81..60e45e48 100644
--- a/test/static/unit_test.cpp
+++ b/test/static/unit_test.cpp
@@ -36,10 +36,10 @@ using percent_ = struct percent;
 
 // base dimensions
 // clang-format off
-inline constexpr struct dim_length_ : base_dimension<"L"> {} dim_length;
-inline constexpr struct dim_mass_ : base_dimension<"M"> {} dim_mass;
-inline constexpr struct dim_time_ : base_dimension<"T"> {} dim_time;
-inline constexpr struct dim_thermodynamic_temperature_ : base_dimension<symbol_text{u8"Θ", "O"}> {} dim_thermodynamic_temperature;
+inline constexpr struct dim_length_ final : base_dimension<"L"> {} dim_length;
+inline constexpr struct dim_mass_ final : base_dimension<"M"> {} dim_mass;
+inline constexpr struct dim_time_ final : base_dimension<"T"> {} dim_time;
+inline constexpr struct dim_thermodynamic_temperature_ final : base_dimension<symbol_text{u8"Θ", "O"}> {} dim_thermodynamic_temperature;
 
 // quantities specification
 QUANTITY_SPEC_(length, dim_length);