TypeScript - filter type keys by value

example.ts

type Thing = {
  a: number
  b: number
  c: string
  d: boolean
}

type Values<O> = O[keyof O]

type KeysWithType<O, T> = Values<{ [K in keyof O]: O[K] extends T ? K : never }>

type ThingNumberKeys = KeysWithType<Thing, number> // a | b

function doThing(key: KeysWithType<Thing, number>, thing: Thing) {
  return thing[key]
}