Hide macro replacement

include/cppast/code_generator.hpp

@@ -160,6 +160,7 @@ namespace cppast
             exclude_return, //< Exclude the return type of a function entity.
             exclude_target, //< Exclude the underlying entity of an alias (e.g. typedef).
             declaration,    //< Only write declaration.
+            /// For a macro, it won't show the replacement if this flag is set
             _flag_set_size, //< \exclude
         };