Strongly typed promisify utility function

Promisfy.ts

type ErrorFirstCallback<D> = (error: any, data: D) => void;

type FunctionThatAcceptsCallback<A extends any[], D> = (
  ...args: [...A, ErrorFirstCallback<D>]
) => void;

type FunctionThatReturnsPromise<A extends any[], D> = (...args: A) => Promise<D>

function promisify<A extends any[], D>(
  originalFunction: FunctionThatAcceptsCallback<A, D>
): FunctionThatReturnsPromise<A, D> {
  return (...args: A) => {
    return new Promise((resolve, reject) => {
      originalFunction(...args, (error, data) => {
        if (error) {
          reject(error);
        } else {
          resolve(data);
        }
      });
    });
  };
}

function readFile(
  path: string,
  callback: (error: Error | null, fileContents: string) => void
) {
  callback(null, "Fake file data");
}

const readFilePromiseVersion = promisify(readFile);