Union

#[derive(Union)] generates variant accessor methods for enums: is_*(), as_*(), and to_*().

use moxy::Union;

#[derive(Union)]
enum Shape {
    Circle(f64),
    Rect { width: f64, height: f64 },
    Point,
}

This generates:

• is_circle(), is_rect(), is_point() — boolean predicates
• as_circle(), as_rect() — borrow variant data as Option<&T> or Option<(&T1, &T2)>
• to_circle(), to_rect() — clone variant data as Option<T> or Option<(T1, T2)>

Unit variants only get is_*() since there is no data to access.

Attribute Helpers

Use #[moxy(variant(...))] on individual variants:

use moxy::Union;

#[derive(Union)]
enum Token {
    #[moxy(variant(alias = "ident"))]
    Identifier(String),
    #[moxy(variant(skip))]
    Eof,
}

let t = Token::Identifier("foo".into());
assert!(t.is_ident());
assert_eq!(t.as_ident(), Some(&"foo".to_string()));

See Also

• Variant Methods — return types for each variant kind
• Common Fields — auto-detected shared field accessors
• unionize! — shorthand macro for generating union-type enums