<blockquote>
<p dir="auto">Issue originally reported by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/nicolo-ribaudo/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/nicolo-ribaudo">@nicolo-ribaudo</a> in <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="238411555" data-permission-text="Title is private" data-url="https://github.com/babel/babylon/issues/591" data-hovercard-type="issue" data-hovercard-url="/babel/babylon/issues/591/hovercard" href="https://github.com/babel/babylon/issues/591">babel/babylon#591</a></p>
</blockquote>

<h3 dir="auto">Input Code</h3>

<div class="highlight highlight-source-js notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="(a, a) =&gt; b"><pre class="notranslate"><span class="pl-kos">(</span><span class="pl-s1">a</span><span class="pl-kos">,</span> <span class="pl-s1">a</span><span class="pl-kos">)</span> <span class="pl-c1">=&gt;</span> <span class="pl-s1">b</span></pre></div>
<h3 dir="auto">Expected Behavior</h3>
<p dir="auto">Babylon should throw something like <code class="notranslate">Argument name clash in arrow function</code></p>
<h3 dir="auto">Current Behavior</h3>
<p dir="auto"><code class="notranslate">Argument name clash in strict mode</code> (even if that code is not in strict mode)</p>
<h3 dir="auto">Your Environment</h3>

<table role="table">
<thead>
<tr>
<th>software</th>
<th>version</th>
</tr>
</thead>
<tbody>
<tr>
<td>Babylon</td>
<td>7.0.0-beta.14, 6.25.0</td>
</tr>
</tbody>
</table>
<p dir="auto"><a href="https://github.com/ai/browserslist">browserslist</a> provides a way for projects to describe the browsers they need to support which is then used by tools like Autoprefixer to generate the appropriate CSS for that set of browsers.</p>
<p dir="auto">6to5 could use this metadata + <a href="https://www.npmjs.com/package/caniuse-db" rel="nofollow">caniusedb</a> to selectively transpile features based on browser support.</p>