Rust Expert Best Practices

Simple, pragmatic, opinionated. Only what matters for writing production-grade Rust code.

When to Apply

Reference these guidelines when:

• Writing Rust code (structs, functions, enums, traits)
• Implementing error handling and Result types
• Reviewing Rust code for safety or performance issues
• Refactoring existing Rust codebases
• Designing APIs and public interfaces
• Optimizing Rust code for performance or clarity

Rule Categories by Priority

Priority	Category	Impact	Prefix
1	Type Safety	CRITICAL	use-typesafe-, use-enum-
2	Error Handling	CRITICAL-HIGH	result-, avoid-panic
3	API Design	HIGH	use-borrowed-, prefer-builder-
4	Code Quality	MEDIUM-HIGH	use-iterator-, prefer-format
5	Readability	MEDIUM	use-named-, avoid-boolean-
6	Performance	MEDIUM	avoid-rc, avoid-box

Quick Reference

• use-borrowed-argument-types - Use &str, &[T], &Path instead of &String, &Vec, &PathBuf
• use-enum-deserialization - Use exhaustive enum matching for safe deserialization
• use-typesafe-index-wrappers - Wrap index types to prevent mixing different indices
• result-error-returns - Use ? operator instead of unwrap/expect in Result functions
• avoid-panic - Use assert!, Result, or expect based on context instead of panic!
• use-iterator-transforms - Use iterator methods instead of explicit push loops
• use-copied - Use .copied() to avoid complex dereferencing patterns
• prefer-format - Use format! over manual string concatenation
• prefer-builder-pattern-for-complex - Use builder pattern for functions with 4+ parameters
• use-named-placeholders - Use named placeholders instead of bare _ in destructuring
• decimal-comparison - Use .is_sign_negative() instead of comparing to Decimal::ZERO
• calculated-field-as-method - Implement calculated fields as methods not struct fields
• avoid-rc - Avoid unnecessary Rc when simpler ownership patterns work
• avoid-box - Don't use Box for concrete types without legitimate reason
• avoid-boolean-params - Replace boolean parameters with enums or structs
• match-statements-handle-all-cases - Explicitly handle all enum variants without catch-all patterns

How to Use

Read individual rule files for detailed explanations and code examples:

rules/use-borrowed-argument-types.md
rules/use-enum-deserialization.md
rules/use-typesafe-index-wrappers.md
rules/result-error-returns.md
rules/avoid-panic.md
rules/use-iterator-transforms.md
rules/use-copied.md
rules/prefer-format.md
rules/prefer-builder-pattern-for-complex.md
rules/use-named-placeholders.md
rules/decimal-comparison.md
rules/calculated-field-as-method.md
rules/avoid-rc.md
rules/avoid-box.md
rules/avoid-boolean-params.md
rules/match-statements-handle-all-cases.md

Each rule file contains:

• Brief explanation of why it matters
• When to use and when not to use the pattern
• Implementation requirements
• BAD code examples with explanation
• GOOD code examples with explanation
• Additional context and best practices