Make JSON_BRACE_INIT_COPY_SEMANTICS part of the ABI tag

The macro changes the body of the initializer-list constructor and adds a
to_json_tuple_impl overload, both with the same mangled names in either
mode, so mixing translation units silently picked one definition. Encode
it in the inline namespace as `_bics`, as JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
does with `_ldvcmp`. The macro is new in the unreleased 3.13.0, so no
existing namespace name changes.

- Move the macro's default into abi_macros.hpp so json_fwd.hpp computes
  the same namespace, and keep it defined under JSON_TEST_KEEP_MACROS.
- Check the tag in the ABI config tests and in the unit test.
- List `_bics` (and the missing `_dp`) in the namespace docs and in the
  natvis generator; regenerate nlohmann_json.natvis.
- Replace the "define it consistently" warning with an ABI note.

Suggested by @gregmarr in the review of #5544.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

include/nlohmann/detail/abi_macros.hpp

@@ -34,6 +34,10 @@
     #define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 0
 #endif
 
+#ifndef JSON_BRACE_INIT_COPY_SEMANTICS
+    #define JSON_BRACE_INIT_COPY_SEMANTICS 0
+#endif
+
 #if JSON_DIAGNOSTICS
     #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -52,20 +56,27 @@
     #define NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON
 #endif
 
+#if JSON_BRACE_INIT_COPY_SEMANTICS
+    #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS _bics
+#else
+    #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
+#endif
+
 #ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
     #define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
 #endif
 
 // Construct the namespace ABI tags component
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c) json_abi ## a ## b ## c
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c)
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d) json_abi ## a ## b ## c ## d
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
 
 #define NLOHMANN_JSON_ABI_TAGS                                       \
     NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                       \
             NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
-            NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS)
+            NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS,              \
+            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
 
 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

include/nlohmann/detail/macro_scope.hpp

@@ -804,10 +804,6 @@ void templated_json_throw(ExceptionType exception)
     #define JSON_USE_GLOBAL_UDLS 1
 #endif
 
-#ifndef JSON_BRACE_INIT_COPY_SEMANTICS
-    #define JSON_BRACE_INIT_COPY_SEMANTICS 0
-#endif
-
 #ifndef JSON_STRICT_NUL_HANDLING
     #define JSON_STRICT_NUL_HANDLING 0
 #endif

include/nlohmann/detail/macro_unscope.hpp

@@ -26,7 +26,6 @@
 #undef JSON_NO_UNIQUE_ADDRESS
 #undef JSON_DISABLE_ENUM_SERIALIZATION
 #undef JSON_USE_GLOBAL_UDLS
-#undef JSON_BRACE_INIT_COPY_SEMANTICS
 #undef JSON_STRICT_NUL_HANDLING
 
 #ifndef JSON_TEST_KEEP_MACROS
@@ -45,6 +44,7 @@
     #undef JSON_HAS_STD_FORMAT
     #undef JSON_HAS_STATIC_RTTI
     #undef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+    #undef JSON_BRACE_INIT_COPY_SEMANTICS
 #endif
 
 #include <nlohmann/thirdparty/hedley/hedley_undef.hpp>