Use array of string literals to discriminate union

[florianbepunkt]

I have a distinct set of operations, represented as a a string literal Operation. Some operations require additional data/props, so I would like to create a type, that based on whether the array contains a certain operation, includes these additional properties.

I'm not sure if this is even possible to express in Typescript.

What I have so far (not working pseudo-code):

type Operator = "A" | "B" | "C" | "D";

type StructWithAorD = {
  operators: Operator[];
  propOnlyForAorD: string;
};

type StructWithB = {
  operators: Operator[];
  propOnlyForB: string;
};

type StructWithC = {
  operators: Operator[];
};

type Struct = StructWithAorD | StructWithB | StructWithC;

declare const a: Struct = {
  operators: ["A"],
  propOnlyForAorD: "", // this should be mandatory if and only if operators array includes "A" one or several times (regardless of order)
};

declare const b: Struct = {
  operators: ["B"],
  propOnlyForB: "", // this should be mandatory if and only if operators array includes "B" one or several times (regardless of order)
};

declare const aAndB: Struct = {
  operators: ["A", "B"],
  propOnlyForAorD: "",
  propOnlyForB: "",
};

declare const structs: Struct[];