propType [name] is not required, but has no corresponding defaultProps declaration ReactJS

It’s explained in the documentation: https://reactjs.org/docs/typechecking-with-proptypes.html#default-prop-values

As you are marking this prop as not required it is asking you to put a default in case the prop is missing.

So, something like this (but default values depends on you):

Checkbox.defaultProps = {
  checked: false,
  className: null,
}