After a discussion with @spicyj we decided to keep the warning even though the functions will throw in production. The warning is the only way to learn about that.

We should also document how to pass the secret through in case you know what you're doing.

`Property \`${propFullName}\` of component \`${componentName}\` has invalid PropType notation inside arrayOf.`
      );
    }
    var propValue = props[propName];
    if (!Array.isArray(propValue)) {
      var locationName = ReactPropTypeLocationNames[location];
      var propType = getPropType(propValue);
      return new PropTypeError(
        `Invalid ${locationName} \`${propFullName}\` of type ` +
        `\`${propType}\` supplied to \`${componentName}\`, expected an array.`
      );
    }
    for (var i = 0; i < propValue.length; i++) {
      var error = typeChecker(
        propValue,
        i,
        componentName,
        location,
        `${propFullName}[${i}]`
      );
      if (error instanceof Error) {
        return error;
      }
    }
    return null;
  }
  return createChainableTypeChecker(validate);
}
function createElementTypeChecker() {
  function validate(props, propName, componentName, location, propFullName) {