'Symbol' is undefined in IE11 with Next v5.1.0

• I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior

App should work after upgrading to Next v5.1.0. in Next-js supported browsers.

Current Behavior

Noticed 'Symbol' is undefined issue in IE11 after upgrading to Next v5.1.0. We don’t see this issue with Next v4.x.

Steps to Reproduce (for bugs)

1. Upgrade app, which has for-of loop in its source code, to Nextv5.1.0.
2. Open the application in IE 11 after build process and check the dev console.

Context

This is happening with Next v5.1.0.

Code generated for for-of loop with Next v5.1.0

for (var g = l[Symbol.iterator](), w; !(h = (w = g.next()).done); h = true) {                        
}

Next v4.x version with same source code.

for (var h, g = (0,r.default)(l); !(y = (h = g.next()).done); y = !0) {
}

We can fix the issue by adding babel-polyfill or babel runtime-transform to our code but it would be consistent if we have a solution as part of Next build.

Your Environment

Tech	Version
next	5.1.0
node	8.11.1
OS	windows
browser	IE 11
etc

[timneutkens]

@matejkonrad can you provide a full reproduction? I assume it’s because you have a module in node_modules that uses Symbol

[matejkonrad]

This is an issue for me on Next 7.0.2 on IE11, Windows 10 (using browserstack)