GiveMeThisForChristmasPlease.ts

type AProps = {foo: string, prop?: string};
type BProps = {bar: number};

class A extends React.Component<AProps> {}
class B extends React.Component<BProps> {}

class AB extends React.Component<AProps & BProps> {
  render () {
    const {aProps, bProps} = split(runtime AProps, runtime BProps, this.props);
    return (
      <A {...aProps}>
        <B {...bProps}/>
      </A>
    );
  }
}