test.ts

type CustomType<K extends keyof any> = {
    [P in K]: number
};
type Config<K extends keyof any> = {
    [P in K]?: {
        highPriority: boolean;
        callback: (values: any[]) => number[];
    }
};

declare const customFunction:
    <K extends keyof any>(values: Record<K, any>[], config: Config<K>) => Array<CustomType<K>>

const values = [
  {
    foo: 'foo',
    bar: 'bar'
  },
  {
    foo: 'foo',
    bar: 'bar'
  }
];

const config = {
  foo: {
    highPriority: true,
    callback: () => []
  },
  wrong: {
    highPriority: true,
    callback: () => []
  }
};

// error as desired
const result = customFunction(values, config);