class RSpec::Matchers::BuiltIn::RaiseError

def matches?(given_proc, negative_expectation=false, &block)
  @given_proc = given_proc
  @block ||= block
  @raised_expected_error = false
  @with_expected_message = false
  @eval_block = false
  @eval_block_passed = false
  return false unless Proc === given_proc
  begin
    given_proc.call
  rescue Exception => @actual_error
    if values_match?(@expected_error, @actual_error) ||
       values_match?(@expected_error, actual_error_message)
      @raised_expected_error = true
      @with_expected_message = verify_message
    end
  end
  unless negative_expectation
    warn_about_bare_error! if warn_about_bare_error?
    warn_about_nil_error! if warn_about_nil_error?
    eval_block if ready_to_eval_block?
  end
  expectation_matched?
end