explicitly defined assignment operators wrongly relying on implicit generation

.drone.jsonnet

@@ -32,6 +32,7 @@ local linux_pipeline(name, image, environment, packages = "", sources = [], arch
             commands:
             [
                 'set -e',
+                'echo $DRONE_STAGE_MACHINE',
                 'wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -',
             ] +
             (if sources != [] then [ ('apt-add-repository "' + source + '"') for source in sources ] else []) +
@@ -63,6 +64,7 @@ local macos_pipeline(name, environment, xcode_version = "12.2", osx_version = "c
             environment: environment + { "DEVELOPER_DIR": "/Applications/Xcode-" + xcode_version + ".app/Contents/Developer" },
             commands:
             [
+                'echo $DRONE_STAGE_MACHINE',
                 'export LIBRARY=' + library,
                 './.drone/drone.sh',
             ]
@@ -89,6 +91,7 @@ local windows_pipeline(name, image, environment, arch = "amd64") =
             environment: environment,
             commands:
             [
+                'echo $env:DRONE_STAGE_MACHINE',
                 'cmd /C .drone\\\\drone.bat ' + library,
             ]
         }

include/boost/multi_index/composite_key.hpp

@@ -1,4 +1,4 @@
-/* Copyright 2003-2025 Joaquin M Lopez Munoz.
+/* Copyright 2003-2026 Joaquin M Lopez Munoz.
  * Distributed under the Boost Software License, Version 1.0.
  * (See accompanying file LICENSE_1_0.txt or copy at
  * http://www.boost.org/LICENSE_1_0.txt)
@@ -338,6 +338,7 @@ struct composite_key:
   using super::super;
   composite_key()=default;
   composite_key(const composite_key&)=default;
+  composite_key& operator=(const composite_key&)=default;
 
   const key_extractor_tuple& key_extractors()const{return *this;}
   key_extractor_tuple&       key_extractors(){return *this;}
@@ -586,6 +587,7 @@ struct composite_key_equal_to:
   using super::super;
   composite_key_equal_to()=default;
   composite_key_equal_to(const composite_key_equal_to&)=default;
+  composite_key_equal_to& operator=(const composite_key_equal_to&)=default;
 
   const key_eq_tuple& key_eqs()const{return *this;}
   key_eq_tuple&       key_eqs(){return *this;}
@@ -704,6 +706,7 @@ struct composite_key_compare:
   using super::super;
   composite_key_compare()=default;
   composite_key_compare(const composite_key_compare&)=default;
+  composite_key_compare& operator=(const composite_key_compare&)=default;
 
   const key_comp_tuple& key_comps()const{return *this;}
   key_comp_tuple&       key_comps(){return *this;}
@@ -837,6 +840,7 @@ struct composite_key_hash:private detail::augmented_stdtuple<Hash,Hashes...>
   using super::super;
   composite_key_hash()=default;
   composite_key_hash(const composite_key_hash&)=default;
+  composite_key_hash& operator=(const composite_key_hash&)=default;
 
   const key_hasher_tuple& key_hash_functions()const{return *this;}
   key_hasher_tuple&       key_hash_functions(){return *this;}

test/Jamfile.v2

@@ -38,6 +38,7 @@ project
       <toolset>msvc:<define>_SILENCE_ALL_CXX17_DEPRECATION_WARNINGS
       <toolset>msvc:<cxxflags>/wd4494
       <toolset>gcc-16:<cxxflags>-fno-thread-jumps # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119321
+      <toolset>clang-20:<cxxflags>-Wdeprecated-copy
     ;
 
 obj boost_multi_index_key_supported : check_bmi_key_supported.cpp  ;