problem with try catch on ie8

Description

nodejs@8.1.1
babel-core@6.25.0
babel-preset-babili@0.1.4
babel-preset-env@1.5.2

var babel = require('babel-core');
var env = require('babel-preset-env');
var babili = require('babel-preset-babili');
var t = babel.transformFileSync('code.js', {
	presets: [[env,{"targets":{"browsers":"ie >= 7"}}],babili],
	babelrc: false
});
console.log(t.code);

function a(b){
	try{
		console.log(123);
	} catch(e){}
	b();
}
a(function(){
	console.log(456);
});

node test.js

"use strict";function a(a){try{console.log(123)}catch(a){}a()}a(function(){console.log(456)});

Contributor guide

Tech stack

javascriptnodejs

Domain

build system

Issue type

bug

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

3

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

1-3 hours

Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.

stale

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

clear

Prerequisites

JavaScriptBabel basics

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

20

Research direction

The issue arises when babili minifies a try catch block where the catch variable 'e' gets renamed to 'a', conflicting with the function parameter 'a'. This causes IE8 to throw a syntax error because catch parameter names cannot shadow function parameter names in older IE. To fix, investigate how babili handles catch parameter renaming and ensure it avoids such conflicts, possibly by preserving the original name or using a different renaming strategy for catch parameters. The relevant code is in babili's variable renaming logic, likely in the scope handling of try catch blocks.