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//! ASN.1 `CHOICE` support.

use crate::{Decodable, Encodable, Tag, Tagged};

/// ASN.1 `CHOICE` denotes a union of one or more possible alternatives.
///
/// The types MUST have distinct tags.
///
/// This crate models choice as a trait, with a blanket impl for all types
/// which impl `Decodable + Encodable + Tagged` (i.e. they are modeled as
/// a `CHOICE` with only one possible variant)
// TODO(tarcieri): refactor enum custom derive to use `Choice`
pub trait Choice<'a>: Decodable<'a> + Encodable {
    /// Is the provided [`Tag`] decodable as a variant of this `CHOICE`?
    fn can_decode(tag: Tag) -> bool;
}

impl<'a, T> Choice<'a> for T
where
    T: Decodable<'a> + Encodable + Tagged,
{
    fn can_decode(tag: Tag) -> bool {
        T::TAG == tag
    }
}