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: abstract_state.rs
    path of file: ./repos/diem/language/bytecode-verifier/src/reference_safety
    
    the code of the file until where you have to start completion: // Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

//! This module defines the abstract state for the type and memory safety analysis.
use crate::absint::{AbstractDomain, JoinResult};
use borrow_graph::references::RefID;
use mirai_annotations::{checked_postcondition, checked_precondition, checked_verify};
use move_binary_format::{
    binary_views::FunctionView,
    errors::{PartialVMError, PartialVMResult},
    file_format::{
        CodeOffset, FieldHandleIndex, FunctionDefinitionIndex, LocalIndex, Signatu
    
    fn join(&mut self, state: &AbstractState) -> JoinResult {
        let joined = Self::join_(self, state);
        checked_verify!(joined.is_canonical());
        checked_verify!(self.num_locals == joined.num_locals);
        let locals_unchanged = self
            .iter_locals()
            .all(|idx| self.locals.get(&idx) == joined.locals.get(&idx));
        let borrow_graph_unchanged = self.borrow_graph.leq(&joined.borrow_graph);
        if locals_unchanged && borrow_graph_unchanged {
            JoinResult::Unchanged
        } else {
            *self = joined;
            JoinResult::Changed
        }
    }