Empty type inferred by Object.entries

TypeScript Version: 2.7.1

Search Terms: Object entries empty TS2365

Code

let o: any = {x: 5};

let p = Object.entries(o).map(([k, v]) => v + 1);

Compile command: tsc --lib es2017,es2017.object a.ts

Expected behavior: This should compile without any error, assuming v: any. This was the case for Typescript 2.6.2 at least.

Actual behavior: (3,43): error TS2365: Operator ‘+’ cannot be applied to types ‘{}’ and ‘1’.

Following codes compile without errors:

let o: object = {x: 5};

let p = Object.entries(o).map(([k, v]) => v + 1);

let o: any = {x: 5};

let p = Object.entries(o).map(([k, v]: [any, any]) => v + 1);

[liamness]

As a work-around, and building on the workaround for Object.keys() in this comment, I’ve just made one for Object.entries() too. Obviously only safe to use with objects that you have typed and know that these types can be relied upon.

export const entries = Object.entries as <T>(
  o: T
) => [Extract<keyof T, string>, T[keyof T]][]

edit: Looking at it more, I’m not sure Extract is required / desirable here. Seems to work fine without.

[whbjzzwjxq]

e.g.
type item = 'node' | 'link' | 'media'                
let typeDict: Record<item, string[]> = {
                    node: [],
                    link: [],
                    media: []
                };
Object.entries(typeDict).map(([_type, labels]) => {
           **_type inferred as string but not item here**
})