Trait Require 

pub trait Require<O> {
    type Err;

    // Required method
    fn require(self) -> Result<O, Self::Err>
       where Self: Sized;
}

A trait for tokens that can be compared for equivalence against a reference. A helper trait for ergonomically requiring specific token shapes.

Require is intended for tiny wrappers (e.g., Dot, Comma, ParenOpen) that want a try_into-style API without consuming the token stream. Implementors typically return Ok(output) when the token matches the desired pattern, or Err(Self::Err) to hand the original token (or a custom error type) back to the caller so other logic can handle it.

Example

use tokit::{Require, IdentifierToken};

#[derive(Debug, Clone)]
pub enum Punct {
    Dot,
    Comma,
    Other(String),
}

#[derive(Debug, Clone)]
pub struct Dot(pub Punct);

impl Require<Dot> for Punct {
    type Err = Self;

    fn require(self) -> Result<Dot, Self::Err> {
        match &self {
            Punct::Dot => Ok(Dot(Self::Dot)),
            _ => Err(self),
        }
    }
}

Required Associated Types

type Err

The error type returned when a requirement is not met.

Required Methods

fn require(self) -> Result<O, Self::Err>

where Self: Sized,

Attempts to extract the desired output from the token, returning Err(Self::Err) if not possible.

Implementors