a variable named 'filter' can be incorrectly transformed by transform-runtime plugin

[bcutler-work]

Bug Report

Current Behavior
When @babel/plugin-transform-runtime has corejs set to 3, it can incorrectly transform property access using a variable called filter. (Note: NOT the property filter.)

Actual output:

import _filterInstanceProperty from "@babel/runtime-corejs3/core-js-stable/instance/filter";
var filter = 'foo';
var bar = {
  foo: function () {
    return 'foo';
  }
};
console.log(_filterInstanceProperty(bar).call(bar));

Input Code

var filter = 'foo';
var bar = { foo: function() { return 'foo';}};

console.log(bar[filter]());

Expected behavior/code

Expected output: (if corejs is set to false, this is the output, as expected)

var filter = 'foo';
var bar = {
  foo: function () {
    return 'foo';
  }
};
console.log(bar[filter]());

Babel Configuration

module.exports = (api) => {
  api.cache(true);
  return {
    'plugins': [
      ['@babel/plugin-transform-runtime', {
        'corejs': 3,
        'regenerator': true,
        'useESModules': true
      }]
    ],
  };
};

Environment

• Babel version(s): (@babel/cli 7.5.0) (@babel/core 7.5.4) (@babel/plugin-transform-runtime 7.5.0)
• Node/npm version: Node 10.13/npm 6.4.1/yarn 1.15.2
• OS: OSX 10.13.6
• Monorepo: N/A
• How you are using Babel: cli for this example, but it was manifesting the same way with webpack

Additional context/Screenshots
Add any other context about the problem here. If applicable, add screenshots to help explain.

[babel-bot]

Hey @bcutler-work! 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.

[nicolo-ribaudo]

If anyone wants to fix this issue, it's a problem here:

babel/packages/babel-plugin-transform-runtime/src/index.js

Lines 432 to 453 in 5d9a786

	exit(path) {
	if (!injectCoreJS) return;
	if (!path.isReferenced()) return;
	const { node } = path;
	const { object } = node;
	const { name } = object;
	if (!hasMapping(BuiltIns, name)) return;
	if (path.scope.getBindingIdentifier(name)) return;
	path.replaceWith(
	t.memberExpression(
	this.addDefaultImport(
	`${modulePath}/${corejsRoot}/${BuiltIns[name].path}`,
	name,
	),
	node.property,
	node.computed,
	),
	);
	},

If the MemberExpression is computed (i.e. foo[bar]), we need to bail out. We do something similar in the MemberExpression enter visitor, where we handle foo[Symbol.iterator] and then return.

Before working on this issue, please leave a comment to let others know!

If you don't know how to clone Babel, follow these steps: (you need to have make and yarn available on your machine).

1. Write a comment there to know other possible contributors that you are working on this bug.
2. Fork the repo
3. Run git clone https://github.com/<YOUR_USERNAME>/babel.git && cd babel
4. Run yarn && make bootstrap
5. Wait ⏳
6. Run make watch (or make build whenever you change a file)
7. Add a test (only input.js; output.js will be automatically generated)
8. Update the code!
9. yarn jest transform-runtime to run the tests
   • If some test outputs don't match but the new results are correct, you can delete the bad output.js files and run the tests again
10. If it is working, run make test to run all the tests
11. Run git push and open a PR!

[sag1v]

Looks interesting, i would like to try 🙂

[nicolo-ribaudo]

Thanks! If you need any help, you can ask in our slack channel (https://slack.babeljs.io/)