C++ 20 (#2862)

cmake/preproject.cmake

@@ -74,4 +74,4 @@ function(add_warning_checks name)
   )
 endfunction()
 
-set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD 20)

src/kv/kv_types.h

@@ -580,8 +580,6 @@ namespace kv
 
     using NamedHandleMixin::NamedHandleMixin;
     virtual ~AbstractMap() {}
-    virtual bool operator==(const AbstractMap& that) const = 0;
-    virtual bool operator!=(const AbstractMap& that) const = 0;
 
     virtual std::unique_ptr<AbstractCommitter> create_committer(
       AbstractChangeSet* changes) = 0;

src/kv/untyped_map.h

@@ -653,17 +653,13 @@ namespace kv::untyped
       return replicated;
     }
 
-    bool operator==(const AbstractMap& that) const override
+    bool operator==(const Map& that) const
     {
-      auto p = dynamic_cast<const Map*>(&that);
-      if (p == nullptr)
-        return false;
-
-      if (name != p->name)
+      if (name != that.name)
         return false;
 
       auto state1 = roll.commits->get_tail();
-      auto state2 = p->roll.commits->get_tail();
+      auto state2 = that.roll.commits->get_tail();
 
       if (state1->version != state2->version)
         return false;
@@ -706,10 +702,12 @@ namespace kv::untyped
       return ok;
     }
 
-    bool operator!=(const AbstractMap& that) const override
+#ifndef __cpp_impl_three_way_comparison
+    bool operator!=(const Map& that) const
     {
       return !(*this == that);
     }
+#endif
 
     std::unique_ptr<AbstractMap::Snapshot> snapshot(Version v) override
     {