Type 'boolean' is not assignable to type 'never'.ts(2322)

Question

type ZitroneIndexes = keyof Zitrone;

type Zitrone = {
   attr1: any,
   attr2: boolean,
   attr3: number
}

...

objects.forEach((obj: { attr__name: keyof Zitrone; text__: any; attr__type: any; }) => {

switch (obj.attr__type) {
   case "boolean":
       let attribute_name : keyof Zitrone  = obj.attr__name;
       zitrone[attribute_name] = getBool(obj.text__);
   case "int":
       let attribute_name : keyof Zitrone  = obj.attr__name;
       zitrone[attribute_name] = getInt();
   default:
      console.log("object type could not be found.");
  }
});

getBool(bool : string){ // inside of an object so no function keyword
    return bool === 'true';
}
...

I want to use ZitroneIndexes as an dynamic var so i can type obj[attribut] = value.

If ZitroneIndexes is only of type lets say boolean that works. But as soon as i add lets say an MappedType or an keyof where more then one type is present(see type Zitrone), typescript throws the following error:

Type 'boolean' is not assignable to type 'never'.ts(2322)

What did i do wrong? Where can i read more about that?

---

What did you try? -> I did try to switch out types or stuff like ZitroneIndexesBoolean | ZitroneIndexesInt or obj: { attr__name , i reviewed questions on stackoverflow

what were you expecting? -> I expected that an Union or Mapped Type covered that kind of scenario

---

Answer 1

The answer was to cast the type to boolean like this:

(zitrone[attribute_name] as boolean) = getBool(obj.text__);

thx for reading this question everyone