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eval breaks "let" variable declaration scope #10079

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tchaffee opened this issue Jun 10, 2019 · 1 comment

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commented Jun 10, 2019

Bug Report

Current Behavior
Using eval can reveal the underlying Babel transformation and use of var to declare variables that are supposed to have block scope but no longer do.

Input Code

{
  let j = 'privateToBlock';
}

eval('console.log(j)');

Expected behavior/code
In ES6 the above code produces "ReferenceError: j is not defined".

The code transformed using Babel is:

"use strict";

{
  var j = 'privateToBlock';
}
eval('console.log(j)');

Which of course outputs privateToBlock and is unexpected.

Babel Configuration (.babelrc, package.json, cli command)
None

Environment
Using the Babel website.

@babel-bot

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commented Jun 10, 2019

Hey @tchaffee! We really appreciate you taking the time to report an issue. The collaborators
on this project attempt to help as many people as possible, but we're a limited number of volunteers,
so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack
community
that typically always has someone willing to help. You can sign-up here
for an invite.

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