No inferred return type `undefined`

[Timo Rossa]

The function tsuquyomi#hint() doesn't seem to be able to return inferred return types in some cases.
In the following example instead of function add(a: number): number | void it returns function add(a: number): number.

function add(a: number) {
  if (a > 10) return a + 10
}
add(10)