I’m trying to make a generic interface to define a translation dictionary where the primary keys specify the language, and within each language the same keys are present.

Here’s my attempt so far using generics (preferable):

interface TranslationDict<K extends string, O extends K[number]> {
  eng: Record<K, string>;
  jpn: Record<O, string>;
}

const translationDict: TranslationDict<string, string> = {
  eng: {
    year: "year",
    month: "month",
    day: "day",
    file: "file",
  },
  jpn: {
    year: "年",
    month: "月",
    day: "日",
    file: "ファイル",
    file2: "bla", // I want this to throw a type error
  },
};

Without generics, this works, but seems like way too much boilerplate:

const cols = ["year", "month", "day", "file"] as const;

export const commonCols: {
  eng: Record<(typeof cols)[number], string>;
  jpn: Record<(typeof cols)[number], string>;
} = {
  eng: {
    year: "year",
    month: "month",
    day: "day",
    file: "file",
  },
  jpn: {
    year: "年",
    month: "月",
    day: "日",
    file: "ファイル",
    file2: "bla", // TYPE ERROR
  },
};

How do I use generics to constrain the keys of jpn to be the same as the keys of eng?