**Do you want to request a *feature* or report a *bug*?**

bug

**What is the current behavior?**

The warning for a failure to initialize state when using `getDerivedStateFromProps` is not as clear as it could be.

This component produces the warning:
> MyComponent: Did not properly initialize state during construction. Expected state to be an object, but it was undefined.`

```js
class MyComponent extends React.Component {
  static getDerivedStateFromProps(nextProps, prevState) {
    return null;
  }
  render() {
    return <span>Foo</span>
  }
}
```

The warning can be resolved by adding `state = {}` either in the class definition or the constructor, or by not using `getDerivedStateFromProps`.

See https://github.com/reactjs/reactjs.org/issues/796 for more detail on why this warning message can be counter-intuitive.

Since the [warning is specific](https://github.com/facebook/react/blob/b548b3cd640dbd515f5d67dafc0216bb7ee0d796/packages/react-reconciler/src/ReactFiberClassComponent.js#L509-L510) to the use of `getDerivedStateFromProps` and not triggered by any other state or lifecycle methods, and state initialization isn't required for other state methods like `this.setState`, it would make sense to me to mention `getDerivedStateFromProps` explicitly in the warning.

Here's a proposal for a new warning message:
> MyComponent: Component state must be initialized when using getDerivedStateFromProps. Expected state to be an object, but it was undefined.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**

React >= 16.3.0

'instance: you may have forgotten to define `render`.',
          name,
        );
      }
    }
    const noGetInitialStateOnES6 =
      !instance.getInitialState ||
      instance.getInitialState.isReactClassApproved ||
      instance.state;
    warningWithoutStack(
      noGetInitialStateOnES6,
      'getInitialState was defined on %s, a plain JavaScript class. ' +
        'This is only supported for classes created using React.createClass. ' +
        'Did you mean to define a state property instead?',
      name,
    );
    const noGetDefaultPropsOnES6 =
      !instance.getDefaultProps ||
      instance.getDefaultProps.isReactClassApproved;
    warningWithoutStack(
      noGetDefaultPropsOnES6,
      'getDefaultProps was defined on %s, a plain JavaScript class. ' +
        'This is only supported for classes created using React.createClass. ' +
        'Use a static property to define defaultProps instead.',
      name,
    );
    const noInstancePropTypes = !instance.propTypes;
    warningWithoutStack(
      noInstancePropTypes,
      'propTypes was defined as an instance property on %s. Use a static ' +