ts-example-3.ts

// Great to express "something" in your app.
type Point = {
  x: number
  y: number
}

// Great to make your function params easy to understand
function drawPoint (point: Point) {
  // do stuff
}

/**
 * Express that the union of two types becomes
 * something new.
 */
type ProgramError = {
  ok: false
  code: string
  message: string
}

type ProgramSuccess = {
  ok: true
  message: string
}

type ProgramStatus = ProgramError | ProgramSuccess; 

Should this not be:
type Point = {

type ProgramError = {

etc.

Should this not be: type Point = {

type ProgramError = {

etc.

Yes, it should be like that

Damn, you can't be ever too careful, thanks for the catch !