fix: inline restored for non-template constexpr global variables

docs/blog/posts/2.1.0-released.md

@@ -49,19 +49,19 @@ As a side effect, we introduced a :boom: **breaking change** :boom:. We can't us
 hertz anymore:
 
 ```cpp
-constexpr struct hertz : named_unit<"Hz", 1 / second, kind_of<isq::frequency>> {} hertz;
+inline constexpr struct hertz : named_unit<"Hz", 1 / second, kind_of<isq::frequency>> {} hertz;
 ```
 
 and have to type either:
 
 ```cpp
-constexpr struct hertz : named_unit<"Hz", one / second, kind_of<isq::frequency>> {} hertz;
+inline constexpr struct hertz : named_unit<"Hz", one / second, kind_of<isq::frequency>> {} hertz;
 ```
 
 or
 
 ```cpp
-constexpr struct hertz : named_unit<"Hz", inverse(second), kind_of<isq::frequency>> {} hertz;
+inline constexpr struct hertz : named_unit<"Hz", inverse(second), kind_of<isq::frequency>> {} hertz;
 ```
 
 To be consistent, we applied the same change to the dimensions and quantity
@@ -70,13 +70,13 @@ specifications definitions. Now, to define a _frequency_ we have to type:
 === "C++23"
 
     ```cpp
-    constexpr struct frequency : quantity_spec<inverse(period_duration)> {} frequency;
+    inline constexpr struct frequency : quantity_spec<inverse(period_duration)> {} frequency;
     ```
 
 === "C++20"
 
     ```cpp
-    constexpr struct frequency : quantity_spec<frequency, inverse(period_duration)> {} frequency;
+    inline constexpr struct frequency : quantity_spec<frequency, inverse(period_duration)> {} frequency;
     ```
 
 === "Portable"
@@ -145,11 +145,11 @@ If we derive from the same instantiation of `absolute_point_origin` we end up wi
 point origin. This change allows us to provide different names for the same temperature points:
 
 ```cpp
-constexpr struct absolute_zero : absolute_point_origin<absolute_zero, isq::thermodynamic_temperature> {} absolute_zero;
-constexpr struct zeroth_kelvin : decltype(absolute_zero) {} zeroth_kelvin;
+inline constexpr struct absolute_zero : absolute_point_origin<absolute_zero, isq::thermodynamic_temperature> {} absolute_zero;
+inline constexpr struct zeroth_kelvin : decltype(absolute_zero) {} zeroth_kelvin;
 
-constexpr struct ice_point : relative_point_origin<absolute_zero + 273.15 * kelvin> {} ice_point;
-constexpr struct zeroth_degree_Celsius : decltype(ice_point) {} zeroth_degree_Celsius;
+inline constexpr struct ice_point : relative_point_origin<absolute_zero + 273.15 * kelvin> {} ice_point;
+inline constexpr struct zeroth_degree_Celsius : decltype(ice_point) {} zeroth_degree_Celsius;
 ```
 
 Please note that this is a :boom: **breaking change** :boom: as well.

docs/blog/posts/2.2.0-released.md

@@ -281,21 +281,21 @@ is why it was renamed to `symbol_text` (:boom: **breaking change** :boom:).
 === "Now"
 
     ```cpp
-    constexpr struct ohm final : named_unit<symbol_text{u8"Ω", "ohm"}, volt / ampere> {} ohm;
+    inline constexpr struct ohm final : named_unit<symbol_text{u8"Ω", "ohm"}, volt / ampere> {} ohm;
     ```
 
 === "Before"
 
     ```cpp
-    constexpr struct ohm : named_unit<basic_symbol_text{"Ω", "ohm"}, volt / ampere> {} ohm;
+    inline constexpr struct ohm : named_unit<basic_symbol_text{"Ω", "ohm"}, volt / ampere> {} ohm;
     ```
 
 !!! note
 
     On C++20-compliant compilers it should be enough to type the following in the unit's definition:
 
     ```cpp
-    constexpr struct ohm final : named_unit<{u8"Ω", "ohm"}, volt / ampere> {} ohm;
+    inline constexpr struct ohm final : named_unit<{u8"Ω", "ohm"}, volt / ampere> {} ohm;
     ```
 
 
@@ -307,31 +307,31 @@ marked `final` (:boom: **breaking change** :boom:).
 === "Now"
 
     ```cpp
-    constexpr struct dim_length final : base_dimension<"L"> {} dim_length;
-    constexpr struct length final : quantity_spec<dim_length> {} length;
+    inline constexpr struct dim_length final : base_dimension<"L"> {} dim_length;
+    inline constexpr struct length final : quantity_spec<dim_length> {} length;
 
-    constexpr struct absolute_zero final : absolute_point_origin<isq::thermodynamic_temperature> {} absolute_zero;
-    constexpr auto zeroth_kelvin  = absolute_zero;
-    constexpr struct kelvin final : named_unit<"K", kind_of<isq::thermodynamic_temperature>, zeroth_kelvin> {} kelvin;
+    inline constexpr struct absolute_zero final : absolute_point_origin<isq::thermodynamic_temperature> {} absolute_zero;
+    inline constexpr auto zeroth_kelvin  = absolute_zero;
+    inline constexpr struct kelvin final : named_unit<"K", kind_of<isq::thermodynamic_temperature>, zeroth_kelvin> {} kelvin;
 
-    constexpr struct ice_point final : relative_point_origin<quantity_point{273'150 * milli<kelvin>}> {} ice_point;
-    constexpr auto zeroth_degree_Celsius = ice_point;
-    constexpr struct degree_Celsius final : named_unit<symbol_text{u8"℃", "`C"}, kelvin, zeroth_degree_Celsius> {} degree_Celsius;
+    inline constexpr struct ice_point final : relative_point_origin<quantity_point{273'150 * milli<kelvin>}> {} ice_point;
+    inline constexpr auto zeroth_degree_Celsius = ice_point;
+    inline constexpr struct degree_Celsius final : named_unit<symbol_text{u8"℃", "`C"}, kelvin, zeroth_degree_Celsius> {} degree_Celsius;
     ```
 
 === "Before"
 
     ```cpp
-    constexpr struct dim_length : base_dimension<"L"> {} dim_length;
-    constexpr struct length : quantity_spec<dim_length> {} length;
+    inline constexpr struct dim_length : base_dimension<"L"> {} dim_length;
+    inline constexpr struct length : quantity_spec<dim_length> {} length;
 
-    constexpr struct absolute_zero : absolute_point_origin<absolute_zero, isq::thermodynamic_temperature> {} absolute_zero;
-    constexpr struct zeroth_kelvin : decltype(absolute_zero) {} zeroth_kelvin;
-    constexpr struct kelvin : named_unit<"K", kind_of<isq::thermodynamic_temperature>, zeroth_kelvin> {} kelvin;
+    inline constexpr struct absolute_zero : absolute_point_origin<absolute_zero, isq::thermodynamic_temperature> {} absolute_zero;
+    inline constexpr struct zeroth_kelvin : decltype(absolute_zero) {} zeroth_kelvin;
+    inline constexpr struct kelvin : named_unit<"K", kind_of<isq::thermodynamic_temperature>, zeroth_kelvin> {} kelvin;
 
-    constexpr struct ice_point : relative_point_origin<quantity_point{273'150 * milli<kelvin>}> {} ice_point;
-    constexpr struct zeroth_degree_Celsius : decltype(ice_point) {} zeroth_degree_Celsius;
-    constexpr struct degree_Celsius : named_unit<symbol_text{u8"℃", "`C"}, kelvin, zeroth_degree_Celsius> {} degree_Celsius;
+    inline constexpr struct ice_point : relative_point_origin<quantity_point{273'150 * milli<kelvin>}> {} ice_point;
+    inline constexpr struct zeroth_degree_Celsius : decltype(ice_point) {} zeroth_degree_Celsius;
+    inline constexpr struct degree_Celsius : named_unit<symbol_text{u8"℃", "`C"}, kelvin, zeroth_degree_Celsius> {} degree_Celsius;
     ```
 
 Please also note, that the `absolute_point_origin` does not use CRTP idiom anymore (:boom: **breaking change** :boom:).
@@ -509,13 +509,13 @@ conversion factor. Here is a comparison of the code with previous and current de
 === "Now"
 
     ```cpp
-    constexpr struct yard final : named_unit<"yd", mag_ratio<9'144, 10'000> * si::metre> {} yard;
-    constexpr struct foot final : named_unit<"ft", mag_ratio<1, 3> * yard> {} foot;
+    inline constexpr struct yard final : named_unit<"yd", mag_ratio<9'144, 10'000> * si::metre> {} yard;
+    inline constexpr struct foot final : named_unit<"ft", mag_ratio<1, 3> * yard> {} foot;
     ```
 
 === "Before"
 
     ```cpp
-    constexpr struct yard : named_unit<"yd", mag<ratio{9'144, 10'000}> * si::metre> {} yard;
-    constexpr struct foot : named_unit<"ft", mag<ratio{1, 3}> * yard> {} foot;
+    inline constexpr struct yard : named_unit<"yd", mag<ratio{9'144, 10'000}> * si::metre> {} yard;
+    inline constexpr struct foot : named_unit<"ft", mag<ratio{1, 3}> * yard> {} foot;
     ```

docs/index.md

@@ -33,7 +33,7 @@ The library source code is hosted on [GitHub](https://github.com/mpusz/mp-units)
 
     using namespace mp_units;
 
-    constexpr struct smoot final : named_unit<"smoot", mag<67> * usc::inch> {} smoot;
+    inline constexpr struct smoot final : named_unit<"smoot", mag<67> * usc::inch> {} smoot;
 
     int main()
     {
@@ -53,7 +53,7 @@ The library source code is hosted on [GitHub](https://github.com/mpusz/mp-units)
 
     using namespace mp_units;
 
-    constexpr struct smoot final : named_unit<"smoot", mag<67> * usc::inch> {} smoot;
+    inline constexpr struct smoot final : named_unit<"smoot", mag<67> * usc::inch> {} smoot;
 
     int main()
     {

docs/users_guide/framework_basics/character_of_a_quantity.md

@@ -97,15 +97,15 @@ enumeration can be appended to the `quantity_spec` describing such a quantity ty
 === "C++23"
 
     ```cpp
-    constexpr struct position_vector final : quantity_spec<length, quantity_character::vector> {} position_vector;
-    constexpr struct displacement final : quantity_spec<length, quantity_character::vector> {} displacement;
+    inline constexpr struct position_vector final : quantity_spec<length, quantity_character::vector> {} position_vector;
+    inline constexpr struct displacement final : quantity_spec<length, quantity_character::vector> {} displacement;
     ```
 
 === "C++20"
 
     ```cpp
-    constexpr struct position_vector final : quantity_spec<position_vector, length, quantity_character::vector> {} position_vector;
-    constexpr struct displacement final : quantity_spec<displacement, length, quantity_character::vector> {} displacement;
+    inline constexpr struct position_vector final : quantity_spec<position_vector, length, quantity_character::vector> {} position_vector;
+    inline constexpr struct displacement final : quantity_spec<displacement, length, quantity_character::vector> {} displacement;
     ```
 
 === "Portable"
@@ -126,13 +126,13 @@ character override is needed):
 === "C++23"
 
     ```cpp
-    constexpr struct velocity final : quantity_spec<speed, position_vector / duration> {} velocity;
+    inline constexpr struct velocity final : quantity_spec<speed, position_vector / duration> {} velocity;
     ```
 
 === "C++20"
 
     ```cpp
-    constexpr struct velocity final : quantity_spec<velocity, speed, position_vector / duration> {} velocity;
+    inline constexpr struct velocity final : quantity_spec<velocity, speed, position_vector / duration> {} velocity;
     ```
 
 === "Portable"

docs/users_guide/framework_basics/concepts.md

@@ -219,7 +219,7 @@ implicitly convertible from quantity specification `V`, which means that `V` mus
     However, if we define `mean_sea_level` in the following way:
 
     ```cpp
-    constexpr struct mean_sea_level final : absolute_point_origin<isq::altitude> {} mean_sea_level;
+    inline constexpr struct mean_sea_level final : absolute_point_origin<isq::altitude> {} mean_sea_level;
     ```
 
     then it can't be used as a point origin for _points_ of `isq::length` or `isq::width` as none of them

docs/users_guide/framework_basics/design_overview.md

@@ -60,8 +60,8 @@ For example:
 the following way:
 
 ```cpp
-constexpr struct dim_length final : base_dimension<"L"> {} dim_length;
-constexpr struct dim_time final : 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
@@ -71,19 +71,19 @@ provided in the [quantity specification](../../appendix/glossary.md#quantity_spe
 === "C++23"
 
     ```cpp
-    constexpr struct length final : quantity_spec<dim_length> {} length;
-    constexpr struct time final : quantity_spec<dim_time> {} time;
-    constexpr struct speed final : quantity_spec<length / time> {} speed;
+    inline constexpr struct length final : quantity_spec<dim_length> {} length;
+    inline constexpr struct time final : quantity_spec<dim_time> {} time;
+    inline constexpr struct speed final : quantity_spec<length / time> {} speed;
 
     static_assert(speed.dimension == dim_length / dim_time);
     ```
 
 === "C++20"
 
     ```cpp
-    constexpr struct length final : quantity_spec<length, dim_length> {} length;
-    constexpr struct time final : quantity_spec<time, dim_time> {} time;
-    constexpr struct speed final : quantity_spec<speed, length / time> {} speed;
+    inline constexpr struct length final : quantity_spec<length, dim_length> {} length;
+    inline constexpr struct time final : quantity_spec<time, dim_time> {} time;
+    inline constexpr struct speed final : quantity_spec<speed, length / time> {} speed;
 
     static_assert(speed.dimension == dim_length / dim_time);
     ```
@@ -183,17 +183,17 @@ Quantity specification  can be defined by the user in one of the following ways:
 === "C++23"
 
     ```cpp
-    constexpr struct length final : quantity_spec<dim_length> {} length;
-    constexpr struct height final : quantity_spec<length> {} height;
-    constexpr struct speed final : quantity_spec<length / time> {} speed;
+    inline constexpr struct length final : quantity_spec<dim_length> {} length;
+    inline constexpr struct height final : quantity_spec<length> {} height;
+    inline constexpr struct speed final : quantity_spec<length / time> {} speed;
     ```
 
 === "C++20"
 
     ```cpp
-    constexpr struct length final : quantity_spec<length, dim_length> {} length;
-    constexpr struct height final : quantity_spec<height, length> {} height;
-    constexpr struct speed final : quantity_spec<speed, length / time> {} speed;
+    inline constexpr struct length final : quantity_spec<length, dim_length> {} length;
+    inline constexpr struct height final : quantity_spec<height, length> {} height;
+    inline constexpr struct speed final : quantity_spec<speed, length / time> {} speed;
     ```
 
 === "Portable"
@@ -234,13 +234,13 @@ A unit can be defined by the user in one of the following ways:
 template<PrefixableUnit U> struct kilo_ : prefixed_unit<"k", mag_power<10, 3>, U{}> {};
 template<PrefixableUnit auto U> constexpr kilo_<decltype(U)> kilo;
 
-constexpr struct second final : named_unit<"s", kind_of<isq::time>> {} second;
-constexpr struct minute final : named_unit<"min", mag<60> * second> {} minute;
-constexpr struct gram   final : named_unit<"g", kind_of<isq::mass>> {} gram;
-constexpr auto kilogram = kilo<gram>;
-constexpr struct newton final : named_unit<"N", kilogram * metre / square(second)> {} newton;
+inline constexpr struct second final : named_unit<"s", kind_of<isq::time>> {} second;
+inline constexpr struct minute final : named_unit<"min", mag<60> * second> {} minute;
+inline constexpr struct gram   final : named_unit<"g", kind_of<isq::mass>> {} gram;
+inline constexpr auto kilogram = kilo<gram>;
+inline constexpr struct newton final : named_unit<"N", kilogram * metre / square(second)> {} newton;
 
-constexpr struct speed_of_light_in_vacuum final : named_unit<"c", mag<299'792'458> * metre / second> {} speed_of_light_in_vacuum;
+inline constexpr struct speed_of_light_in_vacuum final : named_unit<"c", mag<299'792'458> * metre / second> {} speed_of_light_in_vacuum;
 ```
 
 The [unit equation](../../appendix/glossary.md#unit-equation) of `si::metre / si::second` results
@@ -346,13 +346,13 @@ For example:
 - the absolute point origin can be defined in the following way:
 
   ```cpp
-  constexpr struct absolute_zero final : absolute_point_origin<isq::thermodynamic_temperature> {} absolute_zero;
+  inline constexpr struct absolute_zero final : absolute_point_origin<isq::thermodynamic_temperature> {} absolute_zero;
   ```
 
 - the relative point origin can be defined in the following way:
 
   ```cpp
-  constexpr struct ice_point final : relative_point_origin<absolute_zero + 273'150 * milli<kelvin>> {} ice_point;
+  inline constexpr struct ice_point final : relative_point_origin<absolute_zero + 273'150 * milli<kelvin>> {} ice_point;
   ```
 
 

docs/users_guide/framework_basics/dimensionless_quantities.md

@@ -113,7 +113,7 @@ that uses a unit that is proportional to the ratio of kilometers per megaparsecs
 units of _length_:
 
 ```cpp
-constexpr struct hubble_constant final :
+inline constexpr struct hubble_constant final :
     named_unit<{u8"H₀", "H_0"}, mag_ratio<701, 10> * si::kilo<si::metre> / si::second / si::mega<parsec>> {} hubble_constant;
 ```
 
@@ -158,10 +158,10 @@ Besides the unit `one`, there are a few other scaled units predefined in the lib
 with dimensionless quantities:
 
 ```cpp
-constexpr struct percent final : named_unit<"%", mag_ratio<1, 100> * one> {} percent;
-constexpr struct per_mille final : named_unit<{u8"‰", "%o"}, mag_ratio<1, 1000> * one> {} per_mille;
-constexpr struct parts_per_million final : named_unit<"ppm", mag_ratio<1, 1'000'000> * one> {} parts_per_million;
-constexpr auto ppm = parts_per_million;
+inline constexpr struct percent final : named_unit<"%", mag_ratio<1, 100> * one> {} percent;
+inline constexpr struct per_mille final : named_unit<{u8"‰", "%o"}, mag_ratio<1, 1000> * one> {} per_mille;
+inline constexpr struct parts_per_million final : named_unit<"ppm", mag_ratio<1, 1'000'000> * one> {} parts_per_million;
+inline constexpr auto ppm = parts_per_million;
 ```
 
 ### Superpowers of the unit `one`
@@ -271,17 +271,17 @@ to the quantity specification:
 === "C++23"
 
     ```cpp
-    constexpr struct angular_measure final : quantity_spec<dimensionless, arc_length / radius, is_kind> {} angular_measure;
-    constexpr struct solid_angular_measure final : quantity_spec<dimensionless, area / pow<2>(radius), is_kind> {} solid_angular_measure;
-    constexpr struct storage_capacity final : quantity_spec<dimensionless, is_kind> {} storage_capacity;
+    inline constexpr struct angular_measure final : quantity_spec<dimensionless, arc_length / radius, is_kind> {} angular_measure;
+    inline constexpr struct solid_angular_measure final : quantity_spec<dimensionless, area / pow<2>(radius), is_kind> {} solid_angular_measure;
+    inline constexpr struct storage_capacity final : quantity_spec<dimensionless, is_kind> {} storage_capacity;
     ```
 
 === "C++20"
 
     ```cpp
-    constexpr struct angular_measure final : quantity_spec<angular_measure, dimensionless, arc_length / radius, is_kind> {} angular_measure;
-    constexpr struct solid_angular_measure final : quantity_spec<solid_angular_measure, dimensionless, area / pow<2>(radius), is_kind> {} solid_angular_measure;
-    constexpr struct storage_capacity final : quantity_spec<storage_capacity, dimensionless, is_kind> {} storage_capacity;
+    inline constexpr struct angular_measure final : quantity_spec<angular_measure, dimensionless, arc_length / radius, is_kind> {} angular_measure;
+    inline constexpr struct solid_angular_measure final : quantity_spec<solid_angular_measure, dimensionless, area / pow<2>(radius), is_kind> {} solid_angular_measure;
+    inline constexpr struct storage_capacity final : quantity_spec<storage_capacity, dimensionless, is_kind> {} storage_capacity;
     ```
 
 === "Portable"
@@ -296,9 +296,9 @@ With the above, we can constrain `radian`, `steradian`, and `bit` to be allowed
 specific quantity kinds only:
 
 ```cpp
-constexpr struct radian final : named_unit<"rad", metre / metre, kind_of<isq::angular_measure>> {} radian;
-constexpr struct steradian final : named_unit<"sr", square(metre) / square(metre), kind_of<isq::solid_angular_measure>> {} steradian;
-constexpr struct bit final : named_unit<"bit", one, kind_of<storage_capacity>> {} bit;
+inline constexpr struct radian final : named_unit<"rad", metre / metre, kind_of<isq::angular_measure>> {} radian;
+inline constexpr struct steradian final : named_unit<"sr", square(metre) / square(metre), kind_of<isq::solid_angular_measure>> {} steradian;
+inline constexpr struct bit final : named_unit<"bit", one, kind_of<storage_capacity>> {} bit;
 ```
 
 but still allow the usage of `one` and its scaled versions for such quantities.

docs/users_guide/framework_basics/faster_than_lightspeed_constants.md

@@ -39,12 +39,12 @@ namespace si {
 
 namespace si2019 {
 
-constexpr struct speed_of_light_in_vacuum final :
+inline constexpr struct speed_of_light_in_vacuum final :
   named_unit<"c", mag<299'792'458> * metre / second> {} speed_of_light_in_vacuum;
 
 }  // namespace si2019
 
-constexpr struct magnetic_constant final :
+inline constexpr struct magnetic_constant final :
   named_unit<{u8"μ₀", "u_0"}, mag<4> * mag_pi * mag_power<10, -7> * henry / metre> {} magnetic_constant;
 
 }  // namespace mp_units::si