treaty -


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// pub mod protocols;
// pub mod walkers;

use crate::protocol::Visitor;

/// A type that can be walked.
pub trait Walk<'ctx>: Sized {
    /// The walker for the type.
    type Walker: Walker<'ctx> + From<Self>;
}

/// Walker for a type.
///
/// The `'ctx` lifetime is some lifetime that is longer than `Self`.
/// Data from the value may borrow using `'ctx`.
///
/// The way to use a walker is as follows.
/// - Call [From::from()] with a value to be walked to make a walker.
/// - Call [Self::walk()] to walk the value. Data will be sent to the provided
///     visitor.
pub trait Walker<'ctx> {
    /// Error that can happen while walking the value.
    type Error;

    /// An arbitrary type the walker is left with after walking.
    ///
    /// Its recommended that this is `Self` if the walker is repeatable.
    type Output;

    /// Walk the value.
    ///
    /// The walker should send data to the `visitor` as it walks the value.
    fn walk(self, visitor: Visitor<'_, 'ctx>) -> Result<Self::Output, Self::Error>;
}