Use Meaningful Standard Types

RUST-USE-MEANINGFUL-STANDARD-TYPES

Rust Validation Policy Public API Reader Locality

Summary

Prefer standard or ecosystem types that encode ownership, units, paths, durations, optionality, and invariants better than raw strings or integers. Use domain newtypes when the standard type cannot prevent meaningful mixups.

Rule

Use standard library types that carry meaning.

Why

Standard library types such as PathBuf, NonZeroUsize, Duration, Cow, Arc, and Result carry familiar ownership and invariant signals. Use them when they communicate the contract better than a custom type.

Helps

Helps encode units, ownership, paths, durations, nonzero constraints, borrowing, and optionality directly in function signatures.

Limits

Domain-specific newtypes are better when the standard type cannot express the invariant or when mixing values would be dangerous.

Agent Instruction

Use standard library types that carry meaning because standard library types such as `PathBuf`,
`NonZeroUsize`, `Duration`, `Cow`, `Arc`, and `Result` carry familiar ownership and invariant
signals.

Mechanisms

Prefer Path, Duration, NonZero*, Cow, OsStr, SocketAddr, Url-like ecosystem types, and other meaningful types over raw strings and integers.