Module num_enum

Type-safe conversions between enums and primitive numbers.

• Crate ::num_enum.
• docs.rs
• crates.io
• GitHub

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num_enum provides procedural macros for deriving type-safe conversions between Rust enums and primitive numeric types.

While Rust’s as operator can convert enums to numbers, it can silently truncate values and doesn’t provide safe conversions in the reverse direction. num_enum fills this gap with derive macros that generate conversion implementations with proper error handling.

The primary derives are IntoPrimitive for converting enums to numbers, and TryFromPrimitive for fallible conversion from numbers to enums. For cases where all numeric values map to enum variants, FromPrimitive provides infallible conversion, and UnsafeFromPrimitive offers unsafe transmutation for performance-critical code.

Examples

Basic conversion between enums and numbers:

use num_enum::{IntoPrimitive, TryFromPrimitive};

#[derive(Debug, PartialEq, IntoPrimitive, TryFromPrimitive)]
#[repr(u8)]
enum Status {
    Success = 0,
    Warning = 1,
    Error = 2,
}

// Convert enum to number.
let code: u8 = Status::Warning.into();
assert_eq!(code, 1);

// Convert number to enum.
let status = Status::try_from(2).unwrap();
assert_eq!(status, Status::Error);

// Invalid conversions return an error.
assert!(Status::try_from(99).is_err());

Structs

TryFromPrimitiveError

Traits

FromPrimitive

TryFromPrimitive

UnsafeFromPrimitive

Derive Macros

Default

Implements core::default::Default for a #[repr(Primitive)] enum.

FromPrimitive

Implements From<Primitive> for a #[repr(Primitive)] enum.

IntoPrimitive

Implements Into<Primitive> for a #[repr(Primitive)] enum.

TryFromPrimitive

Implements TryFrom<Primitive> for a #[repr(Primitive)] enum.

UnsafeFromPrimitive

Generates a unsafe fn unchecked_transmute_from(number: Primitive) -> Self associated function.