Pick<> not working in React setState with updater function

[Suzii]

TypeScript Version: 2.4.0 / nightly (2.5.0-dev.201xxxxx)
The React setState(...) function fails to detect incompatible value being returned from an updater function. Pick<> does not seem to work well in this case. I thought this would be fixed in v2.4 but it is not.

The issue migh be related to this one #13359 but it does not seem to be limited to conditional updates.

Code

class MyComponent extends React.PureComponent<{}, { value: string }> {
  _onChange = (event: ChangeEvent<HTMLInputElement>) => {
    const value = event.target.value;

    this.setState({ valueWithTypo: value }); // correctly reports an error
    this.setState(() => ({ valueWithTypo: value })); // does not detect the typo
  };

  render() {
    // some implementation
  }
}

Expected behavior:
Compiler detects wrong return type of the updater function passed to this.setState(...). (Overload which accepts object (not the updater function) reports an error correctly.)

Actual behavior:
Compiler fails to detect wrong return type of the updater function passed to this.setState(...). No error reported even though argument { valueWithTypo: value } is not compatible with state type { value: string }.

[sylvanaar]

I have reduced your problem down to the typing that is causing the problem.

let f:Pick< { value: string }, never> = () => { return { a:1 }}
`

[dakom]

On a related note, it seems the "broken" version here was the best fix for setting via a dynamic index.

Consider this snippet, modelled after the "Multiple Inputs" section at https://facebook.github.io/react/docs/forms.html but with TS where state satisfies a particular interface:

onFormUpdated(evt:React.ChangeEvent<HTMLInputElement>) {
    let name = evt.currentTarget.getAttribute("name");
    let value = evt.currentTarget.value;
    this.setState(() => ({ [name]: value}));
}

Will this break if the issue here is fixed? Is there a cleaner way to write it?

[danthegoodman]

There's been some discussion (but no resolution) of this over in DefinitelyTyped/DefinitelyTyped#18365

[typescript-bot]

This issue has been marked as 'External' and has seen no recent activity. It has been automatically closed for house-keeping purposes.