Recently introduces keyof operator will work well for typing functions that accept properties directly on target type.

interface Some {
  a: number,
  b: string
}

type oneOfTheSomeKeys = keyof Some // restricts value to "a", "b"

What do you think, is it possible in theory to type deeply nested paths, so that for type:

interface Some {
  a: number,
  b: {
    c: number
    d: {
      e: number
    }
  }
}

so that it would be possible to restrict possible path values to:

["a"]
["b"]
["b", "c"]
["b", "d"]
["b", "d, "e"]

This actual for such methods like ramda's path:

R.path(['a', 'b'], {a: {b: 2}}); //=> 2
R.path(['a', 'b'], {c: {b: 2}}); //=> undefined

?