Flow: Cannot setState to value that was initially null - type is incompatible

[Foxhoundn]

There is a modal manager I am transferring to flow in our codebase and it has an initial state -

state = {
  modal: null,
}

When the app changes the state - adds a react element to the modal state value - flow errors with

169:         this.setState({ modal: lastModal });
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ call of method setState
169:         this.setState({ modal: lastModal });
                                    ^^^^^^^^^ React$Element. This type is incompatible with
 27:     modal: null,
                ^^^^ null

The state is typed as follows

state: {
  modal: ?React.Element<any>,
};

[avikchaudhuri]

As a workaround, please cast null to the appropriate type, like

state = {
  modal: (null: ?React.Element<any>),
}

Let us know if it doesn't work. Also, where does the above line appear?

[Foxhoundn]

@avikchaudhuri that worked, although I don't like having so much boilerplate. Why isn't the state type declaration taking this into context?

Thanks

[AugustinLF]

Any news on that? I stumbled onto this case too, here is a small example. @avikchaudhuri's workaround does work, but is that really normal?

[AugustinLF]

This works as expected in 0.53, it can be closed.