Enum as generic param, enforce secondary type

I want to create a type-safe method of assigning secondary keys to an object, depending on the value of a primary type (which is currently an enum). I tried the following, but the type Test is typed as string instead of an union of allowed values. How can I achieve this?

export enum PrimaryImageType {
  Artnum = "ARTNUM",
  RMA = "RMA",
}

export const SecondaryImageTypes: Record<PrimaryImageType, string[]> = {
  [PrimaryImageType.Artnum]: [
    "LDA_OVP",
    "LDA_PALETTE",
    "LDA_LABEL",
    "LDA_VERPACKHINWEIS",
    "LDA_MASTERKARTON",
  ],
  RMA: [
  ],
};

export type SecondaryType<P extends PrimaryImageType> = typeof SecondaryImageTypes[P][number];

type Test =  SecondaryType<PrimaryImageType.Artnum>;
//   Test is typed as string, I expect it to be "LDA_OVP" | "LDA_PALETTE" | "LDA_LABEL" | "LDA_VERPACKHINWEIS" | "LDA_MASTERKARTON"


// I want to use those types similar to this:
export interface Image<P extends PrimaryImageType> {
  id: number,
  imageType: P,
  typeID: string,
  secondaryType: SecondaryType<P>,
}

// TS should enforce the union of secondary types:
const testImg: Image<PrimaryImageType.Artnum> = {
  id: 1,
  imageType: PrimaryImageType.Artnum,
  typeID: "asd",
  secondaryType: "INVALID", // should be invalid
}

Playground Link

You see it as string because you declared SecondaryImageTypes as Record<PrimaryImageType, string[]>, and ts can't narrow the string to the literal values that you have used.

The easiest thing to do is to remove the type definition of SecondaryImageTypes and const assert it:

export const SecondaryImageTypes = {
  [PrimaryImageType.Artnum]: [
    'LDA_OVP',
    'LDA_PALETTE',
    'LDA_LABEL',
    'LDA_VERPACKHINWEIS',
    'LDA_MASTERKARTON',
  ],
  RMA: [],
} as const;

Doing this will solve your problem, however SecondaryImageTypes is not type safe and thanks to satisfies operator we can easily fix it.
Note: satisfies was added in Typescript 4.9 so it will not works for the previous versions.

export const SecondaryImageTypes = {
  [PrimaryImageType.Artnum]: [
    'LDA_OVP',
    'LDA_PALETTE',
    'LDA_LABEL',
    'LDA_VERPACKHINWEIS',
    'LDA_MASTERKARTON',
  ],
  RMA: [],
} as const satisfies Record<PrimaryImageType, readonly string[]>;

// type Test = "LDA_OVP" | "LDA_PALETTE" | "LDA_LABEL" | "LDA_VERPACKHINWEIS" | "LDA_MASTERKARTON"
type Test = SecondaryType<PrimaryImageType.Artnum>;

playground