PropType conditional type inference in TypeScript

PropType.tsx

import { ComponentType } from "react";

/**
 * For any type T that is a React.ComponentType give me the type of its Props
 *
 */
export type PropType<T> = T extends ComponentType<infer P> ? P : never;

// USAGE:
import { Component, Fragment } from "react";

type ButtonProps = {
  color: "blue" | "green";
};

// This can be some button in a third party library or one you want to
// gradually remove from your codebase
const Button: React.SFC<ButtonProps> = () => <button />;

// Your newer button component can leech its prop type and add its own on top
type NewerButtonProps = PropType<typeof Button> & {
  size: "small" | "large";
};

class NewerButton extends Component<NewerButtonProps> {}

const Example = () => (
  <Fragment>
    <Button color="blue" />
    <NewerButton color="green" size="large" />
  </Fragment>
);