plugin-transform-modules-commonjs: export binding not updated by 'for...in' and 'for...of'

Bug Report

• I would like to work on a fix!

Current Behavior If an exported binding is used as LHS in a ForOfStatement or ForInStatement, only the local variable is updated. The exported binding stays the same.

Input Code

• REPL or Repo link if applicable: https://babeljs.io/en/repl#?browsers=&build=&builtIns=false&spec=false&loose=false&code_lz=KYDwDg9gTgLgBAG2PAZhCcC8cDkBLAOzxjwEMEcBuAKGrSjgAo0NC4BvMKCMALjgCMAXwCUHIbXpMWcCCjgBtHMCQBbYARg4AumPYS60JuxZDZ8hSfT8cAE2ABnGFACuAYxguowWziG7xWiA&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&timeTravel=false&sourceType=module&lineWrap=true&presets=es2016&prettier=false&targets=&version=7.7.4&externalPlugins=%40babel%2Fplugin-transform-modules-commonjs%407.7.5

export let foo = 'initial';

for (foo in {prop: 1}) {}

for (foo of ['element']) {}

for ({foo} of [{foo: 'destructured'}]) {}

Expected behavior/code exports.foo should be updated every time foo is assigned a new value. I tested the code without transpilation in Node.js and it works as expected.

[vedantroy]

I’ll take a shot at this.

[vedantroy]

PR: https://github.com/babel/babel/pull/11074