Derive Macro NumericEnum

#[derive(NumericEnum)]

Derive macro that generates bidirectional conversion methods between enum variants and their numeric values. This automatically generates:

• from_int<T: Into<usize>>(value: T) -> Option<Self>: Converts a numeric value to the corresponding enum variant
• to_int(&self) -> usize: Converts the enum variant back to its numeric value

Examples

Basic usage:

use slang_derive::NumericEnum;

#[derive(Debug, PartialEq, NumericEnum)]
enum OpCode {
    Add = 1,
    Subtract = 2,
    Multiply, // Implicit value: 3
    Divide,   // Implicit value: 4
}

// Convert from numeric values to enum variants:
let add_op = OpCode::from_int(1u8); // Some(OpCode::Add)
let add_op_usize = OpCode::from_int(1usize); // Some(OpCode::Add)
let invalid_op = OpCode::from_int(100u8); // None

Both explicit and implicit discriminant values are supported:

use slang_derive::NumericEnum;

#[derive(NumericEnum)]
enum Status {
    Ok = 200,
    NotFound = 404,
    ServerError = 500,
    Created = 201,  // Note: order doesn't matter for explicit values
    NotModified = 304,
    BadRequest = 400,
}