type Merge<T, U> = Omit<T, keyof U> & U;

interface BaseConfig {
  id: string;
  debug: boolean;
  port: number;
}

interface FeatureConfig {
  port: string; // This will override the 'port' from BaseConfig
  apiUrl: string;
  timeout: number;
}

// Resulting type will have FeatureConfig's 'port' type
type MergedConfig = Merge<BaseConfig, FeatureConfig>;

const config: MergedConfig = {
  id: 'abc-123',
  debug: true,
  port: '8080', // Must be string due to FeatureConfig override
  apiUrl: 'https://api.example.com',
  timeout: 5000
};

// console.log(config);