TS compile errors on 4.10.0 - An index signature parameter type must be 'string' or 'number'.

[timothyallan]

Hey all, I'm getting TS compile errors with mobx 4.10.0 and TS 3.4.5 as well as TS 3.5.1
It's related to #1944

../client/node_modules/mobx/lib/types/observableobject.d.ts:37:10 - error TS1023: An index signature parameter type must be 'string' or 'number'.

37         [key: PropertyKey]: ObservableValue<any> | ComputedValue<any>;
            ~~~

[loklaan]

Hi @timothyallan, could you post an abstract of the code that raises these errors when compiled?

[timothyallan]

Yeah I'll look into it some more. It really just was happening while doing a ./node_modules/typescript/bin/tsc -p ./src, but if nobody else is getting that, there must be something else at play

[cameronbraid]

I am getting it too

ERROR in [at-loader] ./node_modules/mobx/lib/types/observableobject.d.ts:37:10
TS1023: An index signature parameter type must be 'string' or 'number'.

[cameronbraid]

export declare class ObservableObjectAdministration implements IInterceptable<IObjectWillChange>, IListenable {
    target: any;
    name: string;
    defaultEnhancer: IEnhancer<any>;
    values: {
        [key: PropertyKey]: ObservableValue<any> | ComputedValue<any>;
    };
`11

[cameronbraid]

Looks like PropertyKey has been changed to include symbol not just string and number

https://github.com/microsoft/TypeScript/blob/master/lib/lib.es5.d.ts#L105

[loklaan]

Oh no, I checked it out, looks like the build of the [email protected] is broken. (shown above) 😭
The change that affected this is mine, my bad 😬.

My recommendation is to stay on [email protected].

---

Looks like the implementation in the mobx4-master branch uses a keyed object instead of a Map, and Symbols aren't yet supported as object keys (check out #microsoft/TypeScript/1863 for progress). I think the intention was to put a @ts-ignore on the line but it gets dropped during the build-step.

Together with #1987, it might be easier to leave out Symbol support for keys for the 4.x release... That's up to the maintainers.

[mweststrate]

Fixed in 4.11.0

[lock]

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