Example of "All members must conform to the string index signature" looks wrong to me

[deqing]

https://basarat.gitbook.io/typescript/type-system/index-signatures#all-members-must-conform-to-the-string-index-signature

/** Error */
interface Bar {
  x: number;
  y: string; // ERROR: Property `y` must be of type number
}

Actually this example is not error