Type inference in switch with user-defined type guards

[goodmind]

TypeScript Version: nightly (2.2.0-dev.20161124)

Code

type UpdateMessage = { message: any }
type UpdateInlineQuery = { inline_query: any }
type UpdateCallbackQuery = { callback_query: any }
type Update = UpdateMessage | UpdateInlineQuery | UpdateCallbackQuery 

function isMessage (x: Update): x is UpdateMessage {
  return (<UpdateMessage> x).message !== undefined;
}

function isInlineQuery (x: Update): x is UpdateInlineQuery {
  return (<UpdateInlineQuery> x).inline_query !== undefined;
}

function isCallbackQuery (x: Update): x is UpdateCallbackQuery {
  return (<UpdateCallbackQuery> x).callback_query !== undefined;
}

function checkType(u: Update) {
  switch (true) {
    case isMessage(u):
      console.log('message', u);
      break;
    case isInlineQuery(u):
      console.log('inline query', u);
      break;
    case isCallbackQuery(u):
      console.log('callback query', u)
      break;
    default:
      console.log('unknown type', u)
  }
}

Expected behavior:

case isMessage(u):
  u.bad_type // Property 'bad_type' does not exist on type 'UpdateMessage'.
  console.log('message', u);
  break;
case isInlineQuery(u):
  u.bad_type // Property 'bad_type' does not exist on type 'UpdateInlineQuery'.
  console.log('inline query', u);
  break;

Actual behavior:

case isMessage(u):
  u.bad_type // Property 'bad_type' does not exist on type 'UpdateMessage'.
  console.log('message', u);
  break;
case isInlineQuery(u):
  u.bad_type // Property 'bad_type' does not exist on type 'UpdateMessage'.
  console.log('inline query', u);
  break;

[RyanCavanaugh]

Duplicate #8934