rollup treeshaking breaks es.string.split.js

[AndrewLeedham]

Issue

When using rollup with babel to inject core-js polyfills, the SUPPORTS_Y check gets truncated from

var SUPPORTS_Y = !fails(function () { RegExp(MAX_UINT32, 'y'); });

to

var SUPPORTS_Y = !fails(function () {  });

rollup seems to see this as having no side-effects and tree-shakes it. Whereas in reality the side-effect is an error being thrown.

Repro

I created a minimal repro to showcase that toggling treeshaking through rollup is causing the issue: https://codesandbox.io/s/r0vj2k7znn. See line 22 on the dest/output-*.js files.

Possible Solution

Perhaps this is an issue for rollup. But a quick fix would be to just return the RegExp call:

var SUPPORTS_Y = !fails(function () { return RegExp(MAX_UINT32, 'y'); });
// or
var SUPPORTS_Y = !fails(function () { return new RegExp(MAX_UINT32, 'y'); });

[zloirock]

Seems it an issue for rollup. However, I can add a fallback on core-js side.

[AndrewLeedham]

Thanks for adding the workaround @zloirock. Much appreciated. Is there any plan to release a beta version with this in?