function assertUnfrozen(name, frozen) {
  if (frozen) {
    throw new Error(
      'Cannot call `' +
        name +
        '` on a frozen processor.\nCreate a new processor first, by calling it: use `processor()` instead of `processor`.'
    )
  }
}
Assert the processor is not frozen.

@param {string} name
@param {unknown} frozen
@returns {asserts frozen is false}