class Plumb::Build

def _inspect = "Build[#{@type.inspect}]"

def call(result) = result.valid(@block.call(result.value))

def initialize(type, factory_method: :new, &block)
  @type = type
  @block = block || ->(value) { type.send(factory_method, value) }
  @children = [type].freeze
  freeze
end