Example of babel-plugin-iife-wrap issue when combined with babel-plugin-transform-es2015-typeof-symbol.

gulpfile.js

'use strict';

const gulp = require('gulp');
const babel = require('gulp-babel');

gulp.task('default', () =>
    gulp.src('iife-bug-reproduction.js')
        .pipe(babel({ plugins: [

            // To make it work, either comment out this one...
            'iife-wrap',

            require('babel-plugin-transform-es2015-template-literals'),
            require('babel-plugin-transform-es2015-literals'),
            require('babel-plugin-transform-es2015-function-name'),
            require('babel-plugin-transform-es2015-arrow-functions'),
            require('babel-plugin-transform-es2015-block-scoped-functions'),
            require('babel-plugin-transform-es2015-classes'),
            require('babel-plugin-transform-es2015-object-super'),
            require('babel-plugin-transform-es2015-shorthand-properties'),
            require('babel-plugin-transform-es2015-duplicate-keys'),
            require('babel-plugin-transform-es2015-computed-properties'),
            require('babel-plugin-transform-es2015-for-of'),
            require('babel-plugin-transform-es2015-sticky-regex'),
            require('babel-plugin-transform-es2015-unicode-regex'),
            require('babel-plugin-check-es2015-constants'),
            require('babel-plugin-transform-es2015-spread'),
            require('babel-plugin-transform-es2015-parameters'),
            require('babel-plugin-transform-es2015-destructuring'),
            require('babel-plugin-transform-es2015-block-scoping'),

            // ...or this one
            require('babel-plugin-transform-es2015-typeof-symbol'),

            require('babel-plugin-transform-es2015-modules-commonjs'),
            [require('babel-plugin-transform-regenerator'), { async: false, asyncGenerators: false }],
        ]}))
        .pipe(gulp.dest('dist/'))
);

iife-bug-reproduction.js

// My example es2015 code with typeof Symbol
// Babel will transpile this just fine, if either the iife-wrap plugin or the 
// transform-es2015-typeof-symbol plugin are commented out, but will not work
// if they are both present

// iife-wrap seems to make transform-es2015-typeof-symbol run twice on the same
// code but I am not sure exactly what is going on

// See for yourself.  Download these three files, put them in a folder, then run
// `npm install && npm start`.  It will error.  Then comment out one of the two
// plugins identified by my comments in the gulpfile.  Try `npm start` again and
// watch it compile successfullly.

let mySymbol = Symbol('foo');

console.log(typeof mySymbol);

package.json

{
  "name": "iife-bug-reproduction",
  "version": "1.0.0",
  "main": "index.js",
  "license": "ISC",
  "scripts": {
    "start": "gulp && echo '--- BUILD DONE ---' && node dist/iife-bug-reproduction.js"
  },
  "dependencies": {
    "babel-plugin-iife-wrap": "^1.1.0",
    "babel-preset-es2015": "^6.6.0",
    "gulp": "^3.9.1",
    "gulp-babel": "^6.1.2"
  }
}