Intl.Segments.prototype.containing should include undefined in return value

[Jamesernator]

⚙ Compilation target

ESNext

⚙ Library

ESNext

Missing / Incorrect Definition

The interface Intl.Segments lacks an undefined in the return type for containing:

interface Segments {
    // Should be SegmentData | undefined
    containing(codeUnitIndex?: number): SegmentData;
}

Sample Code

const segmenter = new Intl.Segmenter();

const segments = segmenter.segment("Hello world");
// @ts-expect-error This should report an error
const s: Intl.SegmentData = segments.containing(40);
// This should be fine
const s: Intl.SegmentData | undefined = segments.containing(40);

Documentation Link

MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Segmenter/segment/Segments/containing#return_value