TypeScript で再帰的な type が定義できる条件がわからない

gistfile1.ts

// OK
type T = {
  [key: string]: T
}

// OK
type U = {
  foo: U
} & (() => string)

// Type alias 'V' circularly references itself.
type V = {
  [key: string]: V
} & (() => string)

// OK
type W = {
  [key: string]: WInterface
} & (() => string)

interface WInterface extends W {}

microsoft/TypeScript#33050 🤔