<p dir="auto">Comment placement not preserved in the following:</p>
<p dir="auto"><strong>source</strong></p>
<div class="highlight highlight-source-js notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="// no args
function foo(/* some comment */) {
}"><pre class="notranslate"><span class="pl-c">// no args</span>
<span class="pl-k">function</span> <span class="pl-en">foo</span><span class="pl-kos">(</span><span class="pl-c">/* some comment */</span><span class="pl-kos">)</span> <span class="pl-kos">{</span>
<span class="pl-kos">}</span></pre></div>
<p dir="auto"><strong>6to5 v2.12.0</strong></p>
<div class="highlight highlight-source-js notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="&quot;use strict&quot;;

function foo() {}
/* some comment */
"><pre class="notranslate"><span class="pl-s">"use strict"</span><span class="pl-kos">;</span>

<span class="pl-k">function</span> <span class="pl-en">foo</span><span class="pl-kos">(</span><span class="pl-kos">)</span> <span class="pl-kos">{</span><span class="pl-kos">}</span>
<span class="pl-c">/* some comment */</span></pre></div>
<hr>
<p dir="auto">This works though:</p>
<div class="highlight highlight-source-js notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="// have args
function foo( arg /* some comment */) {
}
function foo( /* some comment */ arg) {
}"><pre class="notranslate"><span class="pl-c">// have args</span>
<span class="pl-k">function</span> <span class="pl-en">foo</span><span class="pl-kos">(</span> <span class="pl-s1">arg</span> <span class="pl-c">/* some comment */</span><span class="pl-kos">)</span> <span class="pl-kos">{</span>
<span class="pl-kos">}</span>
<span class="pl-k">function</span> <span class="pl-en">foo</span><span class="pl-kos">(</span> <span class="pl-c">/* some comment */</span> <span class="pl-s1">arg</span><span class="pl-kos">)</span> <span class="pl-kos">{</span>
<span class="pl-kos">}</span></pre></div>
<p dir="auto">The following example <code class="notranslate">gulpfile</code> runs at <strong>~5.5 seconds</strong> on my machine when processing an empty file.</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="var gulp = require('gulp');
var babel = require('gulp-babel');

var ENTRY_FILE = './test.js';
var BUILD_PATH = './build';

var build = function() {
    return gulp.src(ENTRY_FILE)
        .pipe(babel({ presets: ['es2015']}))
        .pipe(gulp.dest(BUILD_PATH));
};

gulp.task('build', build);

gulp.task('default', ['build']);"><pre class="notranslate"><code class="notranslate">var gulp = require('gulp');
var babel = require('gulp-babel');

var ENTRY_FILE = './test.js';
var BUILD_PATH = './build';

var build = function() {
    return gulp.src(ENTRY_FILE)
        .pipe(babel({ presets: ['es2015']}))
        .pipe(gulp.dest(BUILD_PATH));
};

gulp.task('build', build);

gulp.task('default', ['build']);
</code></pre></div>
<p dir="auto">Package versions:</p>
<ul dir="auto">
<li><code class="notranslate">gulp@3.9.0</code></li>
<li><code class="notranslate">gulp-babel@6.1.0</code></li>
<li><code class="notranslate">babel-preset-es2015@6.1.18</code></li>
</ul>
<p dir="auto">Is this a known issue, or is it just a problem with my environment/machine?</p>