Ruby 2 & 3's keyword args and how `ruby2_keywords` works

ruby_2_and_3_keyword_args.rb

# Helpers to make the code below easier to read
class Array
  def keywords?()    = Hash.ruby2_keywords_hash?(self[-1])
  def to_keywords!() = (self[-1] = Hash.ruby2_keywords_hash(self[-1]))
end

# Code to facilitate the examples below
def record_args(*args) = args
def call_this(val:)    = val

args = record_args val: 123 # => [{:val=>123}]

# It's a normal hash, Ruby won't pass it into the keywords slot
args.keywords?            # => false
call_this *args rescue $! # => #<ArgumentError: wrong number of arguments (given 1, expected 0; required keyword: val)>

# We can explicitly turn it into a keywords hash
call_this *args rescue $! # => #<ArgumentError: wrong number of arguments (given 1, expected 0; required keyword: val)>
args.to_keywords!
call_this *args           # => 123

# `ruby2_keywords` modifies the method to implicitly do what we did above
record_args(val: 1).keywords? # => false
ruby2_keywords :record_args
record_args(val: 1).keywords? # => true