I have a function createUnion that takes an array of callbacks with different return types and returns one of the results. I want it to return a union of the return types. It works perfectly when combining types with null or undefined, but not other types. They are not even done in order precedence. How can I correctly infer the union type from all the callbacks?

function createUnion <Creation> (creators: Array<() => Creation>): Creation {
  const index = Math.floor(Math.random() * creators.length)
  const creator = creators[index]
  const creation = creator()
  return creation
}

function createNumber (): number {
  return 42
}

function createString (): string {
  return 'Hello'
}

function createNull (): null {
  return null
}

function createUndefined (): undefined {
  return undefined
}

function createBoolean (): boolean {
  return true
}

// Correctly typed as string | null
export const stringOrNull = createUnion([
  createString,
  createNull
])

// Correctly typed as number | undefined
export const numberOrUndefined = createUnion([
  createNumber,
  createUndefined
])

// Incorrectly typed as string
export const stringOrNumber = createUnion([
  createString,
  createNumber // Type '() => number' is not assignable to type '() => string'.
  // Type 'number' is not assignable to type 'string'.ts(2322)
])

// Incorrectly typed as string
export const numberOrString = createUnion([
  createNumber, // Type '() => number' is not assignable to type '() => string '.
  createString
])

// Incorrectly typed as number
export const numberOrBoolean = createUnion([
  createBoolean, // Type '() => boolean' is not assignable to type '() => number'.
  // Type 'boolean' is not assignable to type 'number'.ts(2322)
  createNumber
])