A computed property name in an interface must directly refer to a built-in symbol

[nbransby]

TypeScript Version: 2.1

When will TypeScript be able to type check this:

const location = Symbol("Quick reply location")
const onText = Symbol("Text message responder")
const onLocation = Symbol("Location message responder")
const onImage = Symbol("Image message responder")

interface ResponseHandler {
    [quickReply: string]: () => void
    [location](lat: number, long: number): void
    [onText](text: string): void;
    [onLocation](lat: number, long: number): void;
    [onImage](url: string): void;
}

What I would like it to do is verify the methods defined on an object conforming to this interface have the right parameters based on the property symbol / type (in case of string)

[aluanhaddad]

How would an implementation acquire the symbol for say, location?

[nbransby]

let handler: ResponseHandler = {
        [location](lat: number, long: number) {
            console.log(`User located at ${lat}, ${long}`);            
        }
    }

[aluanhaddad]

And where does that symbol come from? Is it something exported by the module that exports the interface?

[nbransby]

Yes it is defined above the interface in the example

[mhegazy]

Duplicate of #5579

[aluanhaddad]

@nbransby right, of course! for some reason I thought you were using modules. I don't know why, as you do not in your example.
Regardless, since each instantiation of a non-well-known symbol is unique, it would make it impossible for consumers to implement the interface without acquiring the original instantiation. Perhaps that is desirable in your use case though.

[nbransby]

Yes thats exactly the use case im after. My example is non-module based for simplicity but the symbols would be exported with the interface