function defaultMessage(site) {
  var callSite = site.callSite
  var funcName = site.name
  var typeName = callSite.getTypeName()

  // make useful anonymous name
  if (!funcName) {
    funcName = '<anonymous@' + formatLocation(site) + '>'
  }

  // make useful type name
  if (typeName === 'Function') {
    typeName = callSite.getThis().name || typeName
  }

  return callSite.getMethodName()
    ? typeName + '.' + funcName
    : funcName
}
Generate a default message from the site.