evaluate incorrectly evaluates variables to undefined

[mvanderlee]

Describe the bug When minifying angularjs I ran into an issue where valid variables were defined to undefined, and then void 0

To Reproduce

 function ngOptionsPostLink(scope, selectElement, attr, ctrls)
 {
     // if ngModel is not defined, we don't need to do anything
     var ngModelCtrl = ctrls[1];
     if (!ngModelCtrl) return;

     var selectCtrl = ctrls[0];
     var multiple = attr.multiple;

     // The emptyOption allows the application developer to provide their own custom "empty"
     // option when the viewValue does not match any of the option values.
     var emptyOption;
     for (var i = 0, children = selectElement.children(), ii = children.length; i < ii; i++)
     {
         if (children[i].value === '')
         {
             emptyOption = children.eq(i);
             break;
         }
     }
    return emptyOption;
 }

Actual Output

function ngOptionsPostLink(scope, selectElement, attr, ctrls)
{
    var ngModelCtrl = ctrls[1];
    if (ngModelCtrl)
        for (var selectCtrl = ctrls[0], multiple = attr.multiple, i = 0, children = selectElement.children(), ii = (void 0).length; void 0 > i; i++)
            if ('' === (void 0)[i].value)
            {
                (void 0).eq(i);
                break
            }
        return emptyOption
}

Expected Output

function ngOptionsPostLink(scope, selectElement, attr, ctrls)
{
    var ngModelCtrl = ctrls[1];
    if (ngModelCtrl)
    {
        for (var emptyOption, selectCtrl = ctrls[0], multiple = attr.multiple, i = 0, children = selectElement.children(), ii = children.length; i < ii; i++)
            if ('' === children[i].value)
            {
                emptyOption = children.eq(i);
                break
            }
        return emptyOption
    }
}

Configuration 7.0.0 (@babel/core 7.0.0) Babel cli and via grunt.

{
  "presets": [
    ["minify", {
      "builtIns": false,
      "mangle": false,
      "removeConsole": true,
      "removeDebugger": true,
      "evaluate": true
    }]  
  ]
}

[attatrol]

I figured out that the error occures only when both plugins transform-merge-sibling-variables and minify-constant-folding are enabled.

Currently i use workaround that forces minify-constant-folding to run before transform-merge-sibling-variables:

{
  "presets": [
    ["minify", {
      "evaluate": false
    }]  
  ],
  "plugins": [
    ["minify-constant-folding"]
  ]
}

However i'm not sure if the plugins used in minify preset could be rearranged in arbitrary order. In general case plugin order matters.