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EnumerableRef

closed_trait

Trait EnumerableRef 

Source 
pub trait EnumerableRef<'a, EnumRef> {
    // Required method
    fn as_enum_ref(&'a self) -> EnumRef;
}
Expand description

A type that can lend itself to the borrowing enum of its sealed trait.

enumerate implements this for every permitted type and makes for<'a> EnumerableRef<'a, TheSealedTraitRef<'a>> a supertrait. The lifetime is a parameter of the trait rather than of the method, so the higher-ranked bound is nameable in the supertrait list, which is what lets a caller reach the enum from a plain &S:


struct Square;

#[enumerate]
#[sealed(Square)]
trait Shape {}

impl Shape for Square {}

let s = &Square;
match s.as_enum_ref() {
    AnyShapeRef::Square(s) => { /* .. */ }
}

Enumerable cannot do this: into_enum takes self, so reaching the owned enum means owning the value. The borrowing enum is also the cheaper one to pass, being a pointer and a discriminant rather than as large as the biggest permitted type.

Required Methods§

Source

fn as_enum_ref(&'a self) -> EnumRef

Wraps &self in the variant of EnumRef that holds this type.

Dyn Compatibility§

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors§