Move’s generics enable reusable, type-safe code, critical for DeFi protocols handling multiple token types. Intermediate developers must apply constraints like key and store to ensure compatibility with Sui’s object model. Why are generics useful in Move for building reusable DeFi modules? Write a generic Move module for a vault that can store and withdraw any coin type. What constraints ensure the module works with Sui’s coin system?

module vault::generic_vault {
    use sui::object::{Self, UID};
    use sui::coin::{Self, Coin};
    use sui::balance::{Self, Balance};
    use sui::tx_context::{Self, TxContext};
    use sui::transfer;

    struct Vault has key {
        id: UID,
        balance: Balance,
    }

    // Create vault for any coin type
    public entry fun create_vault(ctx: &mut TxContext) {
        let vault = Vault {
            id: object::new(ctx),
            balance: balance::zero(),
        };
        transfer::share_object(vault);
    }

    // Deposit coins into vault
    public entry fun deposit(vault: &mut Vault, coin: Coin) {
        coin::put(&mut vault.balance, coin);
    }

    // Withdraw coins (simplified to sender)
    public entry fun withdraw(
        vault: &mut Vault,
        amount: u64,
        ctx: &mut TxContext
    ) {
        let coin = coin::take(&mut vault.balance, amount, ctx);
        transfer::public_transfer(coin, tx_context::sender(ctx));
    }
}