Warning this code is proof-of-concept quality at best! If you find the idea compelling and would like to contribute to making it something reliably shippable, say hi.
Given a file like this:
import * as React from "react";
interface Props {
  foo: string;
}
class FooComponent extends React.Component<Props> {
  context: {
    store: {
      dispatch: (action: any) => any;
    };
  };
  render() {
    return <strong>Your foo is: {this.props.foo}</strong>;
  }
}This loader will emit new TypeScript with prop & context types added:
import * as React from "react";
import * as PropTypes from "prop-types";
interface Props {
  foo: string;
}
class FooComponent extends React.Component<Props> {
  static propTypes = {
    foo: PropTypes.string.isRequired
  };
  static contextTypes = {
    store: PropTypes.shape({
      dispatch: PropTypes.func.isRequired
    }).isRequired
  };
  context: {
    store: {
      dispatch: Function;
    };
  };
  render() {
    return <strong>Your foo is: {this.props.foo}</strong>;
  }
}Look ma! no repetition!