bitflags2-derive

bitflags2-derive provides the #[flags] procedural macro used by the bitflags2 crate.

Most users should depend on bitflags2 instead of this crate directly:

[dependencies]
bitflags2 = "0.1"

What this crate does

The #[flags] macro accepts an enum declaration and expands it into an integer-backed flag type. Variant-level #[flag] markers are parsed by the macro and are not standalone attributes.

use bitflags2::flags;

#[flags]
enum Permission {
    #[flag]
    None = 0,
    #[flag(Read | Write)]
    All,
    #[flag]
    Read,
    #[flag]
    Write,
}

assert_eq!(Permission::All, Permission::Read | Permission::Write);

Supported flag expressions

#[flag(...)] supports:

• integer literals, such as #[flag(0x04)]
• variant names, such as #[flag(Read)]
• bitwise OR expressions, such as #[flag(Read | Write | Execute)]
• parenthesized/grouped expressions

Forward references to later variants are supported.

Development

This crate is split into:

• lib.rs — procedural macro entry point
• parse.rs — enum parsing and value resolution
• model.rs — parsed model types
• codegen.rs — generated Rust code