Should putting @observable on a getter produce an error?

[JoshuaKGoldberg]

I have a:

1. Question: Feel free to just state your question. For a quick answer, there are usually people online at our Gitter channel.

I did a silly:

class MyStore {
    @observable
    public value: number;

    @observable // should have been @computed
    public get double() { return this.value * 2; }
}

Should this produce an error? In practice, MyStore.prototype.timeSinceLastUpdated is undefined, as is all its instances.

[mweststrate]

It is not a supported case indeed, so a PR for runtime checks is welcome

[quanganhtran]

Released in 4.2.1