4.9 regression with in operator: object is incorrectly narrowed to never #50954
Description
Bug Report
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🕗 Version & Regression Information
- This changed between versions 4.8 and 4.9
⏯ Playground Link
Playground link with relevant code
💻 Code
export const checkIsTouchDevice = () =>
"ontouchstart" in window ||
"msMaxTouchPoints" in
// ❌ Unexpected TS error: Property 'navigator' does not exist on type 'never'
window.navigator;I've reduced it down to this:
declare const obj: { a: unknown; b: unknown };
"a" in obj ||
"prop" in
// ❌ Unexpected TS error: Property 'b' does not exist on type 'never'
obj.b;