Crate integral_enum

Integral enum

A simple way to define integer-like enums. This macro implements bunch of traits that are usually implemented via looooong derive(..) attribute.

Tour

IntegralEnum

By default IntegralEnum assumes that you want all trait implementations: PartialOrd, Ord, PartialEq, Eq, Debug, Clone, Copy, TryFrom

use integral_enum::IntegralEnum;

#[derive(IntegralEnum)]
pub enum Sex {
    Male,
    Female,
}

assert_ne!(Sex::Male, Sex::Female);
assert!(Sex::Female > Sex::Male);
assert_eq!(Sex::try_from(0), Ok(Sex::Male));
assert_eq!(format!("{:?}", Sex::Male), "Male");
assert_eq!(Sex::Female.clone(), Sex::Female);

But you may disable some implementations by applying the #[enum_disable(..)] attribute (this will fail to compile due to disabled Debug trait implementation):

#[derive(IntegralEnum)]
#[enum_disable(debug)]
pub enum Sex {
    Male,
    Female,
}

assert_eq!(format!("{:?}", Sex::Male), "Male");

This is useful if you want to compose IntegralEnum with some other macro or your own trait implementations, consider example with the thiserror::Error macro (IT IS MARKED AS COMPILE FAIL ONLY DUE TO LACK OF thiserror DEPENDENCY):

use integral_enum::IntegralEnum;
use thiserror::Error;

#[derive(IntegralEnum, Error)]
pub enum SendError {
    #[error("The remote side is closed connection")]
    Closed,

    #[error("Client with specified id was not found")]
    NotFound,
}

StrictIntegralEnum

On the other hand you may want to enable certain implementations, here the StrictIntegralEnum serves you:

use integral_enum::StrictIntegralEnum;

#[derive(StrictIntegralEnum)]
#[enum_impl(debug, partial_eq, try_from)]
pub enum Sex {
    Male,
    Female
}

assert_eq!(Sex::try_from(0), Ok(Sex::Male));

There’s no other real use-case other than implementing the try_from, but I left possibility to autoimplement other traits for convenience.

Dependencies

Some traits are depending on others, for example Copy depends on Clone, so, if you disable Clone implementation, then Copy implementation will be disabled too. For strict enums rules are the same, but differs in details: if you enable Clone implementation it will not enable the Copy. So, here the dependencies:

• Clone depends on Copy
• Eq depends on PartialEq
• PartialOrd depends on Eq, Copy
• Ord depends on PartialOrd

Limitations

IntegralEnum tries to determine the discriminant exact type based on the following conditions:

• #[repr(..)] attribute
• deducing by the number of variants

And there’s no type inference, wontfix.

So, macro will generate wrong code if there is no #[repr(..)] or discriminant type will deduced wrongly. It is quite hard to infer exact discriminant type with the only AST data, consider the following examples:

// Deduction is not watching to the enum tag's values
// (it is quite hard or even impossible to do it the correct way as stated above, 
//  since tags are just expressions, whose types we can't precisely infer and it just,
//  overcomplicated? This crate is not a all-in solution, just simple pattern implementation,
//  own type-inference will be overkill)
pub enum U16Tag {
    Tag = 0xFF_FF,
}

Derive Macros

IntegralEnum

Macro that implements bunch of traits. See module-level documentation for more detailed explaination.

StrictIntegralEnum

Strict version of the IntegralEnum, see module-level documentation for more detailed explaination.