TypeScript 3.9 | Advanced Types: Extracts generic types from a class or an interface

ClassInfer.ts

type ClassInfer<I> =
  I extends Promise<infer G>
  ? G
  : never

const promise = new Promise<string>(() => {})

type Type1 = ClassInfer<typeof promise> // string

// https://medium.com/free-code-camp/typescript-curry-ramda-types-f747e99744ab
// https://github.com/millsp/medium/blob/master/types-curry-ramda/src/index.ts