instance method Proc#ruby2_keywords

Marks the proc as passing keywords through a normal argument splat. This should only be called on procs that accept an argument splat (`*args`) but not explicit keywords or a keyword splat. It marks the proc such that if the proc is called with keyword arguments, the final hash argument is marked with a special flag such that if it is the final element of a normal argument splat to another method call, and that method call does not include explicit keywords or a keyword splat, the final element is interpreted as keywords. In other words, keywords will be passed through the proc to other methods.

This should only be used for procs that delegate keywords to another method, and only for backwards compatibility with Ruby versions before 2.7.

This method will probably be removed at some point, as it exists only for backwards compatibility. As it does not exist in Ruby versions before 2.7, check that the proc responds to this method before calling it. Also, be aware that if this method is removed, the behavior of the proc will change so that it does not pass through keywords.

module Mod
  foo = ->(meth, *args, &block) do
    send(:"do_#{meth}", *args, &block)
  end
  foo.ruby2_keywords if foo.respond_to?(:ruby2_keywords)
end