Bug Report

🔎 Search Terms

• contextual narrowing
• type narrowing 4.3
• 4.3

🕗 Version & Regression Information

• This is something that I expected to work after 4.3's Contextual Narrowing for Generics

⏯ Playground Link

Playground link with relevant code

💻 Code

declare const eventType: keyof DocumentEventMap;

document.addEventListener(eventType, (event) => {
  event; // Here `event` is `Event | UIEvent | AnimationEvent | MouseEvent | InputEvent | FocusEvent | CompositionEvent | ... 9 more ... | ClipboardEvent
  if (eventType === `click`) {
    event; // Expected: `event` to be type `MouseEvent`. Actual: It's the union from above.
  }
});

🙁 Actual behavior

Second reference of event is type Event | UIEvent | AnimationEvent | MouseEvent | InputEvent | FocusEvent | CompositionEvent | ... 9 more ... | ClipboardEvent.

🙂 Expected behavior

Second reference of event to be of type MouseEvent.