Declaration Merging

interface User {
	name: string
}

interface User {
	email: string
}

interface User {
	age: number
}

// User now has name, email, AND age!
const user: User = {
	name: 'Alice',
	email: 'alice@example.com',
	age: 30,
}

Declaration Merging Across Modules

// config.ts — must be a module (has an import or export)
declare global {
	interface Config {
		appName: string
	}
}

// theme-config.ts — also a module
declare global {
	interface Config {
		theme: 'light' | 'dark'
	}
}

// main.ts
import './config.ts'
import './theme-config.ts'

// Now Config has both appName AND theme!
const config: Config = {
	appName: 'MyApp',
	theme: 'dark',
}

1. In index.ts, use declare global to declare Config with appName: string
2. In config-augment.ts, use declare global to augment Config with theme: 'light' | 'dark' and maxConnections: number, and make the file a module so it can be imported
3. In index.ts, side-effect import ./config-augment.ts to activate the merge
4. Create a config object with all merged properties (appName, theme, maxConnections)
5. Implement getTheme(config: Config) that returns config.theme
6. Export config and getTheme by name

Completion criteria

• Named exports: config, getTheme
• config.appName is a string; config.theme is 'light' or 'dark'; config.maxConnections is a number
• getTheme(config) returns that theme value
• config-augment.ts is importable as a module