Rust Coding Guidelines (50 Core Rules)

Naming (Rust-Specific)

Rule	Guideline
No get_ prefix	fn name() not fn get_name()
Iterator convention	iter() / iter_mut() / into_iter()
Conversion naming	as_ (cheap &), to_ (expensive), into_ (ownership)
Static var prefix	G_CONFIG for static, no prefix for const

Data Types

Rule	Guideline
Use newtypes	struct Email(String) for domain semantics
Prefer slice patterns	if let [first, .., last] = slice
Pre-allocate	Vec::with_capacity(), String::with_capacity()
Avoid Vec abuse	Use arrays for fixed sizes

Strings

Rule	Guideline
Prefer bytes	s.bytes() over s.chars() when ASCII
Use Cow<str>	When might modify borrowed data
Use format!	Over string concatenation with +
Avoid nested iteration	contains() on string is O(n*m)

Error Handling

Rule	Guideline
Use ? propagation	Not try!() macro
expect() over unwrap()	When value guaranteed
Assertions for invariants	assert! at function entry

Memory

Rule	Guideline
Meaningful lifetimes	'src, 'ctx not just 'a
try_borrow() for RefCell	Avoid panic
Shadowing for transformation	let x = x.parse()?

Concurrency

Rule	Guideline
Identify lock ordering	Prevent deadlocks
Atomics for primitives	Not Mutex for bool/usize
Choose memory order carefully	Relaxed/Acquire/Release/SeqCst

Async

Rule	Guideline
Sync for CPU-bound	Async is for I/O
Don't hold locks across await	Use scoped guards

Macros

Rule	Guideline
Avoid unless necessary	Prefer functions/generics
Follow Rust syntax	Macro input should look like Rust

Deprecated → Better

Deprecated	Better	Since
lazy_static!	std::sync::OnceLock	1.70
once_cell::Lazy	std::sync::LazyLock	1.80
std::sync::mpsc	crossbeam::channel	-
std::sync::Mutex	parking_lot::Mutex	-
failure/error-chain	thiserror/anyhow	-
try!()	? operator	2018

Comment Style

• /// for public item docs, //! for module/crate docs, // for inline comments.
• No decorative separators. Never use Unicode box-drawing characters (─, ━, ═, ──) as comment dividers. This includes patterns like // ── Section ─────────────── in any file (.rs, .toml, .sh, etc.). These are AI slop: invisible in diffs, meaningless to tooling, and a signal of low-quality generated code. Use a plain // Section name or nothing.

Unicode Slop Prohibition

Never output these characters in code, comments, docs, or any file:

• → (U+2192): use -> in prose, or => in match arms (which is already Rust syntax)
• — (U+2014, em dash): use -- or restructure
• – (U+2013, en dash): use -
• • (U+2022): use - list markers
• … (U+2026): use ...
• Curly/smart quotes " " ' ': use straight " '

This applies to .rs, .toml, .md, .sh, .json, .yaml, and every other file type.

Quick Reference

Naming: snake_case (fn/var), CamelCase (type), SCREAMING_CASE (const)
Format: rustfmt (just use it)
Docs: /// for public items, //! for module docs
Lint: #![warn(clippy::all)]

Claude knows Rust conventions well. These are the non-obvious Rust-specific rules.