Typescript: array.map lose literal types

[cevek]

TypeScript Version: 3.1.0-dev.20180906

Search Terms:

Code

interface Item {
    x: number;
    y: 'a' | 'b'
}
var list:Item[] = [].map(it => ({x: 1, y: 'a'}))

Expected behavior:
No error

Actual behavior:
Type 'string' is not assignable to type '"a" | "b"'.

[RyanCavanaugh]

Root cause is #241

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.

[thw0rted]

This will be fixed by #40311, see the comment I just left on #33158.

[DanielRosenwasser]

It won't be fixed by #40311 unfortunately (see the "Future Work" section in the PR writeup)

[thw0rted]

Well crud. This is all my fault, I had a bunch of related tabs open and posted this comment in a few of them where I thought the issue being reported was the same -- this wasn't one of them. Sorry!

[DanielRosenwasser]

Don't sweat it, I had the same enthusiasm at first. 😅