A Complex Union Type

type MyType = "x:a" | "x:b" | "x:c" | "y:d" | "y:f" | "y:g";

const obj = {
  x: [
    { value: 'a', checked: false },
    { value: 'b', checked: false },
    { value: 'c', checked: false },
  ],
  y: [
    { value: 'd', checked: false },
    { value: 'f', checked: false },
    { value: 'g', checked: false },
  ],
} as const;

type ObjKey = keyof typeof obj;
type MyType = `${ObjKey}:${(typeof obj)[ObjKey][number]['value']}`;