refactor(util): migrate util/* SFINAE patterns to C++20 concepts (#7632)

Author: DennisOSRM

include/util/alias.hpp

@@ -142,9 +142,8 @@ template <typename ToNumeric, typename FromAlias> inline ToNumeric from_alias(co
     return {static_cast<ToNumeric>(static_cast<const FromAlias::value_type>(from))};
 }
 
-template <typename ToAlias,
-          typename FromNumeric,
-          typename = std::enable_if_t<!std::is_same<ToAlias, FromNumeric>::value>>
+template <typename ToAlias, typename FromNumeric>
+    requires(!std::is_same_v<ToAlias, FromNumeric>)
 inline ToAlias to_alias(const FromNumeric &from)
 {
     static_assert(std::is_arithmetic<FromNumeric>::value, "Numeric needs to be an arithmetic type");

include/util/filtered_integer_range.hpp

@@ -1,9 +1,9 @@
 #ifndef FILTERED_INTEGER_RANGE_HPP
 #define FILTERED_INTEGER_RANGE_HPP
 
+#include <concepts>
 #include <cstddef>
 #include <iterator>
-#include <type_traits>
 
 namespace osrm::util
 {
@@ -80,11 +80,9 @@ template <typename Integer, typename Filter> class filtered_range
 };
 
 template <typename Integer, typename Filter>
-filtered_range<Integer, Filter> filtered_irange(
-    const Integer first,
-    const Integer last,
-    const Filter &filter,
-    typename std::enable_if<std::is_integral<Integer>::value>::type * = nullptr) noexcept
+filtered_range<Integer, Filter>
+filtered_irange(const Integer first, const Integer last, const Filter &filter) noexcept
+    requires std::integral<Integer>
 {
     return filtered_range<Integer, Filter>(first, last, filter);
 }

include/util/indexed_data.hpp

@@ -11,6 +11,7 @@
 #include <boost/assert.hpp>
 
 #include <array>
+#include <concepts>
 #include <functional>
 #include <iterator>
 #include <limits>
@@ -359,24 +360,20 @@ template <typename GroupBlockPolicy, storage::Ownership Ownership> struct Indexe
                                                       const IndexedDataImpl &index_data);
 
   private:
-    template <typename Iter, typename T>
-    using IsValueIterator = std::enable_if_t<
-        std::is_same<T,
-                     std::remove_const_t<typename std::iterator_traits<Iter>::value_type>>::value>;
-
-    template <typename T = ResultType, typename Iter, typename = IsValueIterator<Iter, ValueType>>
-    std::enable_if<!std::is_same<T, std::string_view>::value, T>::type adapt(const Iter first,
-                                                                             const Iter last) const
+    template <typename T = ResultType, typename Iter>
+        requires std::same_as<std::remove_const_t<typename std::iterator_traits<Iter>::value_type>,
+                              ValueType>
+    T adapt(const Iter first, const Iter last) const
     {
-        return ResultType(first, last);
-    }
-
-    template <typename T = ResultType, typename Iter, typename = IsValueIterator<Iter, ValueType>>
-    std::enable_if<std::is_same<T, std::string_view>::value, T>::type adapt(const Iter first,
-                                                                            const Iter last) const
-    {
-        auto diff = std::distance(first, last);
-        return diff == 0 ? ResultType() : ResultType(&*first, diff);
+        if constexpr (std::is_same_v<T, std::string_view>)
+        {
+            auto diff = std::distance(first, last);
+            return diff == 0 ? ResultType() : ResultType(&*first, diff);
+        }
+        else
+        {
+            return ResultType(first, last);
+        }
     }
 
     template <typename T> using Vector = util::ViewOrVector<T, Ownership>;

include/util/static_rtree.hpp

@@ -454,9 +454,9 @@ class StaticRTree
     /**
      * Constructs an empty RTree for de-serialization.
      */
-    template <typename = std::enable_if<Ownership == storage::Ownership::Container>>
     explicit StaticRTree(const std::filesystem::path &on_disk_file_name,
                          const Vector<Coordinate> &coordinate_list)
+        requires(Ownership == storage::Ownership::Container)
         : m_coordinate_list(coordinate_list.data(), coordinate_list.size()),
           m_objects(mmapFile<EdgeDataT>(on_disk_file_name, m_objects_region))
     {