class RSpec::Mocks::ConstantMutator::DefinedConstantReplacer

def verify_constants_to_transfer!
  return [] unless @transfer_nested_constants
  { @original_value => "the original value", @mutated_value => "the stubbed value" }.each do |value, description|
    unless value.respond_to?(:constants)
      raise ArgumentError,
        "Cannot transfer nested constants for #{@full_constant_name} " +
        "since #{description} is not a class or module and only classes " +
        "and modules support nested constants."
    end
  end
  if Array === @transfer_nested_constants
    @transfer_nested_constants = @transfer_nested_constants.map(&:to_s) if RUBY_VERSION == '1.8.7'
    undefined_constants = @transfer_nested_constants - constants_defined_on(@original_value)
    if undefined_constants.any?
      available_constants = constants_defined_on(@original_value) - @transfer_nested_constants
      raise ArgumentError,
        "Cannot transfer nested constant(s) #{undefined_constants.join(' and ')} " +
        "for #{@full_constant_name} since they are not defined. Did you mean " +
        "#{available_constants.join(' or ')}?"
    end
    @transfer_nested_constants
  else
    constants_defined_on(@original_value)
  end
end