I’ve been putting in a lot of effort recently to find a way to access one property, say propA, of a type or interface into another property of the same type or interface, say propB, so that I can make a type inference that is dependent on the value of propA.

Notice that discriminated unions wouldn’t work here, because the type of propA is actually Record<string, any>, i.e., its keys are dynamic and not pre-defined. Unless there is something I’m missing.

Here is an example of what I had in mind:

type MyType = {
    propA: Record<string, any>;
    propB: keyof MyType["propA"]
}

const example: MyType = {
    propA: {
        name: "Jay",
        age: 20,
    },
    propB: "name" // must be either "name" or "age"
}

Is it even possible?