ci: build fixes

Author: jcelerier

examples/lookup.cpp

@@ -34,7 +34,8 @@ void lookup_api(libremidi::API api, const libremidi::input_port& searched)
   {
     // Check inputs.
     auto ports = midi.get_input_ports();
-    auto res = libremidi::find_closest_port(searched, ports);
+    auto res
+        = libremidi::find_closest_port(searched, std::span<const libremidi::input_port>(ports));
     if (res.found) {
       std::cout << "Found: " << *res.port << "\n";
     }

examples/utils.hpp

@@ -49,9 +49,9 @@ inline std::ostream& operator<<(std::ostream& s, const libremidi::container_iden
     void operator()(libremidi::uuid u) { s << "uuid"; }
     void operator()(std::string u) { s << u; }
     void operator()(uint64_t u) { s << u; }
-    void operator()(std::monostate) { }
+    void operator()(libremidi::monostate) { }
   } vis{s};
-  std::visit(vis, id);
+  visit(vis, id);
   return s;
 }
 
@@ -73,9 +73,9 @@ inline std::ostream& operator<<(std::ostream& s, const libremidi::device_identif
         << std::setfill('0') << std::setw(4) << (res & 0x0000FFFF);
       s.flags(f);
     }
-    void operator()(std::monostate) { }
+    void operator()(libremidi::monostate) { }
   } vis{s};
-  std::visit(vis, id);
+  visit(vis, id);
   return s;
 }
 

include/libremidi/config.hpp

@@ -93,14 +93,19 @@ using midi_bytes = std::vector<unsigned char>;
 #endif
 
 // Use boost::variant2 if available
+#define LIBREMIDI_NO_BOOST_VARIANT2 1
 #if __has_include(<boost/variant2.hpp>) && !defined(LIBREMIDI_NO_BOOST_VARIANT2)
   #if __has_include(<boost/variant2.hpp>)
     #include <boost/variant2.hpp>
+    #define LIBREMIDI_VARIANT_IS_BOOST_VARIANT2
 namespace libremidi_variant_alias = boost::variant2;
-  #else
-    #include <variant>
-namespace libremidi_variant_alias = std;
   #endif
+#endif
+
+#if !defined(LIBREMIDI_VARIANT_IS_BOOST_VARIANT2)
+  #include <variant>
+namespace libremidi_variant_alias = std;
+#endif
 
 namespace libremidi
 {
@@ -134,7 +139,6 @@ using libremidi_variant_alias::in_place_index;
 using libremidi_variant_alias::in_place_type;
 using libremidi_variant_alias::visit;
 }
-#endif
 
 #if __has_include(<midi/universal_packet.h>) && defined(LIBREMIDI_USE_NI_MIDI2)
   #define LIBREMIDI_NI_MIDI2_COMPAT 1

include/libremidi/types.hpp

@@ -5,7 +5,6 @@
 #include <compare>
 #include <cstdint>
 #include <string>
-#include <variant>
 
 NAMESPACE_LIBREMIDI
 {