type OriginalType = {
  key1: { sub1: string; sub2: string };
  key2: { subA: string; subB: string };
};

type ValidKeys = keyof OriginalType;
type ValidSubKeys<K extends ValidKeys> = keyof OriginalType[K];

type FixedLengthArray<T, L extends number> = [T, ...T[]] & { length: L };

type EnforcedRecord<L extends number> = {
  [K in ValidKeys]: FixedLengthArray<ValidSubKeys<K>, L>;
};

const createTable = <T extends { length: number }>(
  cols: T,
  rows: EnforcedRecord<T['length']>
) => {
  return { cols, rows };
};

// Example usage:
const cols = ["a", "b", "c"] as const;
const table = createTable(cols, {
  key1: ['sub1', 'sub2', 'sub1', 'sub1'], // invalid because too long
  key2: ['subA', 'subB', 'sub1'], // invalid because bad key
});