https://bugs.ruby-lang.org/issues/19744

Features

• Namespaces to require/load .rb files
• Namespaces to require extensions
• Supporting autoload
• Reopening existing classes/modules
• Adding hooks to end of class/module definitions
• Defining methods on existing classes/modules
• Eval code string in namespaces
• Top-level methods in namespaces
• Creating Procs in namespaces
• Set the global namespace before running scripts
• Defining singleton methods
• Calling include on existing classes/modules
• Newly added constant separation
• Global variable separation
• Implicit reopen with class/module in namespaces on built-in classes/modules
• Loading C libraries as dependencies of extensions in namespaces

Nothing to do

• Defining singleton methods on existing objects
• Calling extend on global objects with namespaced modules
• Class variables
• Class instance variables

TODOs

• Apply refined definitions on methods defined previously
• Implement basename in C instead of calling rb_funcall in rb_namespace_local_extension
• Update Namespace to contain rb_namespace_t directly instead of having Namespace::Entry
• Initialize refiner module lazily to not make overhead if monkey patches are not done
• Support calling require in methods defined in namespace on non-namespaced threads
• Support remove_const, const_defined, const_added, rb_define_global_const, etc