You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: update_with.rs
    path of file: ./repos/irisia-gui/irisia/src
    
    the code of the file until where you have to start completion: use std::{
    ffi::{OsStr, OsString},
    path::{Path, PathBuf},
};

use smallvec::{Array, SmallVec};

/// Custom update methods.
pub trait UpdateWith<T>: Sized {
    /// Update the state, returns whether
    /// the new state is equivalent to the previous.
    ///
    /// - `updater`: The new state.
    /// - `equality_matters`: Whether the return value is matters.
    ///   If not, there is no overhead returning `false` directly
    ///   without checking the equality.
    /// - `return`: Update result, default be `bool`. Indicates whether
    /// `Self` is updated, o
    
        fn update_with(&mut self, mut updater: $I, equality_matters: bool) -> bool {
            if equality_matters {
                let mut result = true;
                let mut old_elements = self.iter_mut();

                for (old, new) in (&mut old_elements).zip(&mut updater) {
                    result = result && (*old == new);
                    *old = new;
                }

                if old_elements.len() != 0 {
                    result = false;
                    let len = old_elements.len();
                    self.drain(self.len() - len..);
                }

                if let Some(next) = updater.next() {
                    result = false;
                    self.push(next);
                    self.extend(updater);
                }

                result
            } else {
                self.clear();
                self.extend(updater);
                false
            }
        }