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: eqeqeq.rs
    path of file: ./repos/swc/crates/swc_ecma_lints/src/rules
    
    the code of the file until where you have to start completion: use serde::{Deserialize, Serialize};
use swc_common::{errors::HANDLER, Span};
use swc_ecma_ast::*;
use swc_ecma_visit::{noop_visit_type, Visit, VisitWith};

use crate::{
    config::{LintRuleReaction, RuleConfig},
    rule::{visitor_rule, Rule},
};

#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
enum EqEqEqMode {
    Always,
    Never,
}

impl Default for EqEqEqMode {
    fn default() -> Self {
        Self::Always
    }
}

#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct EqeqeqConfig {
    #[serde(default)]
    mode: EqEqEqMode,
}

pub fn eqeqeq(config: &RuleConfig<EqeqeqConfig>) -> Option<Box<dyn Rule>> {
    
    fn check(&self, span: Span, bin_op: &BinaryOp) {
        match bin_op {
            op!("==") => {
                if let EqEqEqMode::Always = self.mode {
                    self.emit_report(span, "==", "===");
                }
            }
            op!("!=") => {
                if let EqEqEqMode::Always = self.mode {
                    self.emit_report(span, "!=", "!==");
                }
            }
            op!("===") => {
                if let EqEqEqMode::Never = self.mode {
                    self.emit_report(span, "===", "==");
                }
            }
            op!("!==") => {
                if let EqEqEqMode::Never = self.mode {
                    self.emit_report(span, "!==", "!=");
                }
            }
            _ => {}
        }
    }