rust-best-practices

---

name: rust-best-practices description: ALWAYS invoke this skill when writing, editing, or generating ANY Rust code. This skill provides comprehensive Rust best practices from 5 authoritative sources (Microsoft guidelines, official API guidelines, style guide, language reference, and design patterns). Use for ALL Rust tasks including: writing new code, reviewing code, refactoring, fixing bugs, designing APIs, error handling, unsafe code, FFI, async patterns, macros, testing, or library development. This skill should be loaded proactively whenever Rust (.rs) files are involved.

Rust Best Practices

A comprehensive collection of Rust guidelines from multiple authoritative sources. Load the relevant reference file(s) based on your current task.

Sources

This skill includes content from 5 ebooks:

1. Pragmatic Rust Guidelines (pragmatic_*) - Microsoft's internal Rust guidelines
2. Rust API Guidelines (apiguide_*) - Official API design checklist
3. Rust Style Guide (styleguide_*) - Official formatting conventions
4. The Rust Reference (rustref_*) - Language specification and semantics
5. Rust Design Patterns (patterns_*) - Idiomatic patterns and anti-patterns

---

Quick Reference: When to Load What

Writing Code (General)

Task	Primary Reference
Naming conventions	apiguide_02_naming.md
Code formatting	styleguide_01_introduction.md
General patterns	pragmatic_08_universal_guidelines.md
Rust idioms	patterns_02_idioms_index.md

API Design

Task	Primary Reference
API design checklist	apiguide_01_checklist.md
Type safety patterns	apiguide_08_type_safety.md
Flexibility patterns	apiguide_07_flexibility.md
Predictability	apiguide_06_predictability.md
Library UX design	pragmatic_12_libraries_ux_guidelines.md
Future proofing	apiguide_11_future_proofing.md

Error Handling

Task	Primary Reference
Error types design	apiguide_03_interoperability.md (C-GOOD-ERR)
Application errors	pragmatic_02_application_guidelines.md
Panic handling	rustref_18_panic.md

Type System

Task	Primary Reference
Type coercions	rustref_29_type_coercions.md
Trait bounds	rustref_28_trait_bounds.md
Type layout	rustref_30_type_layout.md
Lifetime elision	rustref_27_lifetime_elision.md
Special traits	rustref_15_special_types_traits.md

Unsafe Code & Safety

Task	Primary Reference
Safety guidelines	pragmatic_07_safety_guidelines.md
Undefined behavior	rustref_22_undefined_behavior.md
Unsafety overview	rustref_21_unsafety.md
Destructors	rustref_26_destructors.md

FFI & Interop

Task	Primary Reference
FFI guidelines	pragmatic_04_ffi_guidelines.md
ABI details	rustref_24_abi.md
Linkage	rustref_19_linkage.md
Inline assembly	rustref_20_inline_assembly.md

Macros

Task	Primary Reference
Macro design	apiguide_04_macros.md
macro_rules!	rustref_05_macros_by_example.md
Proc macros	rustref_06_procedural_macros.md

Documentation

Task	Primary Reference
Doc comments	apiguide_05_documentation.md
Documentation patterns	pragmatic_03_documentation.md

Performance

Task	Primary Reference
Performance guidelines	pragmatic_06_performance_guidelines.md
Const evaluation	rustref_23_const_eval.md

Library Development

Task	Primary Reference
Building crates	pragmatic_09_libraries_building_guidelines.md
Interoperability	pragmatic_10_libraries_interoperability_guidelines.md
Testing & resilience	pragmatic_11_libraries_resilience_guidelines.md
Release requirements	apiguide_12_necessities.md

Code Formatting

Task	Primary Reference
Module items	styleguide_02_items.md
Statements	styleguide_03_statements.md
Expressions	styleguide_04_expressions.md
Types	styleguide_05_types.md
Cargo.toml	styleguide_07_cargo.md

Pattern Matching

Task	Primary Reference
Pattern syntax	rustref_12_patterns.md

Conditional Compilation

Task	Primary Reference
cfg attributes	rustref_08_conditional_compilation.md

Attributes

Task	Primary Reference
Attribute reference	rustref_10_attributes.md

Design Patterns

Task	Primary Reference
Builder pattern	patterns_29_builder.md
Newtype pattern	patterns_24_newtype.md
RAII guards	patterns_25_raii.md
Command pattern	patterns_22_command.md
Strategy pattern	patterns_26_strategy.md
Visitor pattern	patterns_27_visitor.md
Fold pattern	patterns_30_fold.md
Compose structs	patterns_32_compose_structs.md

Anti-patterns (What NOT to do)

Task	Primary Reference
Borrow checker workarounds	patterns_40_borrow_clone.md
deny(warnings) issues	patterns_41_deny_warnings.md
Deref polymorphism	patterns_42_deref_polymorphism.md

Functional Programming

Task	Primary Reference
FP paradigms in Rust	patterns_44_paradigms.md
Generics as type classes	patterns_45_generics_type_classes.md
Functional optics	patterns_46_optics.md

FFI Patterns & Idioms

Task	Primary Reference
FFI error handling	patterns_18_ffi_errors.md
FFI string handling	patterns_19_ffi_accepting_strings.md
Object-based FFI APIs	patterns_37_ffi_export.md
FFI type wrappers	patterns_38_ffi_wrappers.md

---

Key Guidelines Summary

Error Handling

• Libraries: Use canonical error structs with Backtrace (M-ERRORS-CANONICAL-STRUCTS)
• Applications: May use anyhow/eyre (M-APP-ERROR)
• Panics mean "stop the program" - not for error propagation (M-PANIC-IS-STOP)

Safety

• unsafe only for: novel abstractions, performance (after benchmarking), or FFI (M-UNSAFE)
• All code must be sound - no exceptions (M-UNSOUND)
• unsafe marker only for UB risk, not "dangerous" operations (M-UNSAFE-IMPLIES-UB)

API Design (Rust API Guidelines)

• C-COMMON-TRAITS: Types eagerly implement common traits (Copy, Clone, Eq, Debug, etc.)
• C-CONV-TRAITS: Use From, AsRef, AsMut for conversions
• C-NEWTYPE: Newtypes provide static distinctions
• C-BUILDER: Builders enable construction of complex values
• C-VALIDATE: Functions validate their arguments
• C-SEALED: Sealed traits protect against downstream implementations

Formatting (Rust Style Guide)

• Indent with 4 spaces, no tabs
• Max line width: 100 characters
• Use trailing commas when followed by newlines
• Prefer line comments (//) over block comments

Performance

• Identify hot paths early, create benchmarks (M-HOTPATH)
• Long-running async tasks need yield points (M-YIELD-POINTS)
• Use mimalloc for applications (M-MIMALLOC-APPS)

Libraries

• Features must be additive (M-FEATURES-ADDITIVE)
• Libraries must work out of the box on Tier 1 platforms (M-OOBE)
• Don't leak external types in public APIs (M-DONT-LEAK-TYPES)
• Public futures must be Send (M-TYPES-SEND)

---

All Reference Files

Pragmatic Rust Guidelines (Microsoft)

• pragmatic_01_ai_guidelines.md - AI/agent code patterns
• pragmatic_02_application_guidelines.md - Application-level code
• pragmatic_03_documentation.md - Documentation standards
• pragmatic_04_ffi_guidelines.md - FFI and C interop
• pragmatic_06_performance_guidelines.md - Performance optimization
• pragmatic_07_safety_guidelines.md - Unsafe code and soundness
• pragmatic_08_universal_guidelines.md - General patterns
• pragmatic_09_libraries_building_guidelines.md - Crate structure
• pragmatic_10_libraries_interoperability_guidelines.md - Type leaking, Send/Sync
• pragmatic_11_libraries_resilience_guidelines.md - Testing, mocking
• pragmatic_12_libraries_ux_guidelines.md - API design, builders

Rust API Guidelines (Official)

• apiguide_00_about.md - About the guidelines
• apiguide_01_checklist.md - Quick reference checklist
• apiguide_02_naming.md - Naming conventions
• apiguide_03_interoperability.md - Traits and conversions
• apiguide_04_macros.md - Macro design
• apiguide_05_documentation.md - Documentation
• apiguide_06_predictability.md - Predictable APIs
• apiguide_07_flexibility.md - Flexible APIs
• apiguide_08_type_safety.md - Type safety patterns
• apiguide_09_dependability.md - Reliable APIs
• apiguide_10_debuggability.md - Debug support
• apiguide_11_future_proofing.md - Future compatibility
• apiguide_12_necessities.md - Release requirements

Rust Style Guide (Official)

• styleguide_01_introduction.md - Style overview
• styleguide_02_items.md - Module items
• styleguide_03_statements.md - Statements
• styleguide_04_expressions.md - Expressions
• styleguide_05_types.md - Types and bounds
• styleguide_06_advice.md - Other advice
• styleguide_07_cargo.md - Cargo.toml conventions
• styleguide_08_principles.md - Guiding principles
• styleguide_09_editions.md - Style editions
• styleguide_10_nightly.md - Nightly syntax

The Rust Reference (Official)

• rustref_01_introduction.md - Introduction
• rustref_02_notation.md - Notation
• rustref_03_lexical_structure.md - Lexical structure
• rustref_04_macros.md - Macros overview
• rustref_05_macros_by_example.md - macro_rules!
• rustref_06_procedural_macros.md - Proc macros
• rustref_07_crates.md - Crates and source files
• rustref_08_conditional_compilation.md - cfg attributes
• rustref_09_items.md - Items overview
• rustref_10_attributes.md - Attributes
• rustref_11_statements_expressions.md - Statements/expressions
• rustref_12_patterns.md - Pattern matching
• rustref_13_type_system.md - Type system overview
• rustref_14_types.md - Types
• rustref_15_special_types_traits.md - Special types
• rustref_16_names.md - Names and namespaces
• rustref_17_memory_model.md - Memory model
• rustref_18_panic.md - Panic handling
• rustref_19_linkage.md - Linkage
• rustref_20_inline_assembly.md - Inline assembly
• rustref_21_unsafety.md - Unsafety
• rustref_22_undefined_behavior.md - Undefined behavior
• rustref_23_const_eval.md - Const evaluation
• rustref_24_abi.md - ABI
• rustref_25_runtime.md - Rust runtime
• rustref_26_destructors.md - Destructors
• rustref_27_lifetime_elision.md - Lifetime elision
• rustref_28_trait_bounds.md - Trait bounds
• rustref_29_type_coercions.md - Type coercions
• rustref_30_type_layout.md - Type layout

Rust Design Patterns (Community)

Idioms:

• patterns_01_intro.md - Introduction
• patterns_02_idioms_index.md - Idioms overview
• patterns_03_coercion_arguments.md - Use borrowed types for arguments
• patterns_04_concat_format.md - Concatenating strings with format!
• patterns_05_constructor.md - Constructor idiom
• patterns_06_default_trait.md - The Default trait
• patterns_07_deref.md - Collections are smart pointers
• patterns_08_dtor_finally.md - Finalisation in destructors
• patterns_09_mem_replace.md - mem::take and mem::replace
• patterns_10_on_stack_dispatch.md - On-stack dynamic dispatch
• patterns_11_option_iter.md - Iterating over an Option
• patterns_12_closure_vars.md - Pass variables to closure
• patterns_13_priv_extend.md - Privacy for extensibility
• patterns_14_rustdoc_init.md - Easy doc initialization
• patterns_15_temp_mutability.md - Temporary mutability
• patterns_16_return_consumed.md - Return consumed arg on error

FFI Idioms:

• patterns_17_ffi_idioms_intro.md - FFI idioms intro
• patterns_18_ffi_errors.md - Idiomatic FFI errors
• patterns_19_ffi_accepting_strings.md - Accepting strings in FFI
• patterns_20_ffi_passing_strings.md - Passing strings in FFI

Behavioural Patterns:

• patterns_21_behavioural_intro.md - Behavioural patterns intro
• patterns_22_command.md - Command pattern
• patterns_23_interpreter.md - Interpreter pattern
• patterns_24_newtype.md - Newtype pattern
• patterns_25_raii.md - RAII guards
• patterns_26_strategy.md - Strategy pattern
• patterns_27_visitor.md - Visitor pattern

Creational Patterns:

• patterns_28_creational_intro.md - Creational patterns intro
• patterns_29_builder.md - Builder pattern
• patterns_30_fold.md - Fold pattern

Structural Patterns:

• patterns_31_structural_intro.md - Structural patterns intro
• patterns_32_compose_structs.md - Compose structs
• patterns_33_small_crates.md - Prefer small crates
• patterns_34_unsafe_mods.md - Contain unsafety in small modules
• patterns_35_trait_bounds.md - Custom traits for type bounds

FFI Patterns:

• patterns_36_ffi_patterns_intro.md - FFI patterns intro
• patterns_37_ffi_export.md - Object-based APIs
• patterns_38_ffi_wrappers.md - Type consolidation wrappers

Anti-patterns:

• patterns_39_anti_index.md - Anti-patterns intro
• patterns_40_borrow_clone.md - Clone to satisfy borrow checker
• patterns_41_deny_warnings.md - deny(warnings) anti-pattern
• patterns_42_deref_polymorphism.md - Deref polymorphism

Functional Programming:

• patterns_43_functional_index.md - Functional programming intro
• patterns_44_paradigms.md - Programming paradigms
• patterns_45_generics_type_classes.md - Generics as type classes
• patterns_46_optics.md - Functional optics

Additional Resources:

• patterns_47_resources_index.md - Additional resources
• patterns_48_design_principles.md - Design principles