Monkeypatch to mock this feature https://bugs.ruby-lang.org/issues/16986 but using a Hash#to_struct method.

hash_to_struct.rb

# Usage:
#   my_struct = { alpha: 1, beta: 2, 'charlie' => 3 }.to_struct
#   my_struct.alpha   # => 1
#   my_struct.beta    # => 2
#   my_struct.charlie # => 3
# Remember, to compare structs: `my_struct.to_h == other_struct.to_h`
#
# Usage to get deep structs:
#   my_deep_struct = {
#                      email: 'alice@example.com',
#                      address: {
#                        street: '123 Fake st.',
#                        city:   nil,
#                      },
#                    }.to_struct(deep: true)
#   my_deep_struct.email          # => "alice@example.com"
#   my_deep_struct.address.street # => "123 Fake st."
#   my_deep_struct.address.city   # => nil
#   my_deep_struct.address.city = 'Awesomeland'
#   my_deep_struct.address.city   # => "Awesomeland"
#
# Usage to get "immutable" or frozen structs:
#   frozen_struct         = { alpha: 1, beta: 2, 'charlie' => 3 }.to_frozen_struct
#   frozen_struct.charlie = 42 # => FrozenError (can't modify frozen #<Class:0x0...>)
class Hash
  def to_struct(deep: false)
    the_keys = keys.sort_by(&:to_s)
    the_values = values_at(*the_keys)
    the_values = recursively_convert_to_struct(the_values) if deep

    Struct.new(*the_keys).new(*the_values)
  end

  def to_frozen_struct(deep: false)
    recursively_freeze(
      Marshal.load(Marshal.dump(self)).to_struct(deep: deep)
    )
  end

  private

  def recursively_freeze(object)
    if object.respond_to?(:each_pair)
      object.each_pair do |_key, value|
        value = recursively_freeze(value)
      end
    elsif object.respond_to?(:each)
      object.each do |obj|
        obj = recursively_freeze(obj)
      end
    end

    object.freeze
  end

  def recursively_convert_to_struct(values)
    return values.to_struct(deep: true) if values.respond_to?(:to_struct)

    if values.respond_to?(:map)
      return values.map { |v| recursively_convert_to_struct(v) }
    end

    values
  end
end

Done! Thanks @elia, I made some renaming as well.