content: // @flow
  
  import React from 'react';
  
  class Foo extends React.Component<{bar: number}, void> {
    static defaultProps = {bar: 42};
  }
  
  <Foo bar={42}/>; // OK
  <Foo bar="42"/>; // Error
  <Foo bar={undefined}/>; // OK: React will replace `undefined` with the default.
  