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4.1 Array.isArray breaking change review #41808
Description
Categorizing breaks we've seen from this
type Comparable = string | undefined | Array<string>;
export function check<T extends Comparable>(a: T) {
if (Array.isArray(a)) {
// 4.0: m: string
// 4.1: Error, cannot index
const m = a[0];
}
}const aggregatedResults: (number[] | null | 'loading')[] = [[1, 2], null, [3, 4], 'loading', [5, 6]]
// 4.0: onlyTheArrays: number[][]
// 4:1 Error, no overload matches this
const onlyTheArrays = aggregatedResults.filter<number[]>(Array.isArray) // number[][]
Activity
Undo microsoft#39258 (isArray changes) see overview at microsoft#41808
Undo microsoft#39258 (isArray changes) see overview at microsoft#41808
Undo #39258 (isArray changes) see overview at #41808 (#41849)
Undo #39258 (isArray changes) see overview at #41808 (#41851)
jameswilddev commentedon Dec 13, 2020
Hello! Can I just confirm this is fixed in 4.1.3 (released two days ago) as hinted above? I'm having difficulty upgrading from 4.1.2 to 4.1.3 as Array.isArray guard behaviour has changed and want to make sure that any changes I'm making are correct and not mitigations for a (temporary) tool bug.
RyanCavanaugh commentedon Dec 14, 2020
Correct, 4.1.3 contains the revert