Function warnOnInvalidCallback

packages/react-server/src/ReactFizzClassComponent.js:47–63

(callback: mixed)

}

function warnOnInvalidCallback(callback: mixed) {
  if (__DEV__) {
    if (callback === null || typeof callback === 'function') {
      return;
    }
    // eslint-disable-next-line react-internal/safe-string-coercion
    const key = String(callback);
    if (!didWarnOnInvalidCallback.has(key)) {
      didWarnOnInvalidCallback.add(key);
      console.error(
        'Expected the last optional `callback` argument to be a ' +
          'function. Instead received: %s.',
        callback,
      );
    }
  }
}

function warnOnUndefinedDerivedState(type: any, partialState: any) {
  if (__DEV__) {