derive_more

derive_more is the Swiss-army knife of Rust derive macros, with 200M+ all-time downloads. It generates trait implementations for enums, structs, and newtypes across four categories: conversions, formatting, error handling, and operators. It is particularly valuable for the newtype pattern and enums wrapping inner types.

Conversions

• From, Into, TryFrom, TryInto — automatic conversion impls between wrapper types and their inner types
• FromStr — parse strings into types
• IntoIterator — make types iterable

Display and formatting

• Display, Binary, Octal, LowerHex, UpperHex — format types with configurable templates

Error handling

• Error — generates std::error::Error implementations with automatic source and backtrace detection from field types and names. Supports no_std except for provide() (which requires Backtrace from std). A viable alternative to thiserror when you want one derive crate for multiple traits rather than a dedicated error-handling crate. For structured context beyond basic derives, snafu or error-stack remain the better choices. See rust-error-crate-comparison.

Operators

• Arithmetic: Add, Sub, Mul, Div, Rem
• Unary: Not, Neg
• Assign: AddAssign, SubAssign, etc.
• Index: Index, IndexMut
• Deref: Deref, DerefMut

Utility methods

• Constructor — generate new() methods
• IsVariant — is_variant() methods for enums
• Unwrap — unwrap_variant() methods (panics on wrong variant)
• TryUnwrap — try_unwrap_variant() returning Result

The IsVariant, Unwrap, and TryUnwrap derives overlap with enum-as-inner's accessor methods but are bundled into a single dependency.

When to use derive_more

Use derive_more when you need trait derivation across multiple categories — conversions, formatting, operators — from a single crate. For enum-specific ergonomics (iteration, string conversion, metadata), strum is more focused. For error types specifically, thiserror is the ecosystem standard with wider adoption. See rust-enum-crates for the full landscape.