class RSpec::Matchers::BuiltIn::YieldProbe

def assert_valid_expect_block!
  block_signature = RSpec::Support::BlockSignature.new(@block)
  return if RSpec::Support::StrictSignatureVerifier.new(block_signature, [self]).valid?
  raise 'Your expect block must accept an argument to be used with this ' \
        'matcher. Pass the argument as a block on to the method you are testing.'
end