sui-move-syntax

1. Module Layout

Use the new single-line module declaration without braces:

// ✅
module my_package::my_module;

// ❌ Legacy — do not use
module my_package::my_module {
    ...
}

Standard section order within a module:

1. use imports
2. Constants (const)
3. Structs / Enums
4. fun init (if needed)
5. Public functions
6. public(package) functions
7. Private functions
8. Test module (#[test_only])

Use === Section Title === comments to delimit sections for readability.

use import rules

Don't use a lone {Self} — just import the module directly:

// ✅
use my_package::my_module;

// ❌ Redundant braces
use my_package::my_module::{Self};

When importing both the module and members, group them with Self:

// ✅
use sui::coin::{Self, Coin};

// ❌ Separate imports
use sui::coin;
use sui::coin::Coin;

---

2. Mutability — mut is Required

All variables that are reassigned or mutably borrowed must be declared let mut:

// ✅
let mut pool = Pool { id: object::new(ctx), ... };
let mut balance = balance::zero<SUI>();

// ❌ Legacy
let pool = Pool { id: object::new(ctx), ... };

Function parameters that are mutably borrowed must also be mut:

public fun deposit(mut pool: Pool, coin: Coin<SUI>): Pool { ... }

---

3. Visibility

Keyword	Scope
public	Callable from any module
public(package)	Callable only within the same package
(none)	Private — callable only within the same module

public(friend) and friend declarations are deprecated. Use public(package) instead.

// ✅
public(package) fun internal_logic(pool: &mut Pool) { ... }

// ❌ Deprecated
friend my_package::other_module;
public(friend) fun internal_logic(pool: &mut Pool) { ... }

Never use public entry — use one or the other. public functions are composable in PTBs and return values; entry functions are transaction endpoints only and cannot return values: